Update Javadoc snippets for static resource locations

Switch to FileUrlResource, the same as what is used get with
the "file:" prefix in webmvc and webflux config.

See gh-33712

framework-docs/modules/ROOT/pages/web/webflux-functional.adoc

@@ -835,7 +835,7 @@ Java::
 +
 [source,java,indent=0,subs="verbatim,quotes"]
 ----
-    Resource location = new FileSystemResource("public-resources/");
+    Resource location = new FileUrlResource("public-resources/");
     RouterFunction<ServerResponse> resources = RouterFunctions.resources("/resources/**", location);
 ----
 
@@ -843,7 +843,7 @@ Kotlin::
 +
 [source,kotlin,indent=0,subs="verbatim,quotes"]
 ----
-    val location = FileSystemResource("public-resources/")
+    val location = FileUrlResource("public-resources/")
     val resources = router { resources("/resources/**", location) }
 ----
 ======

framework-docs/modules/ROOT/pages/web/webmvc-functional.adoc

@@ -813,7 +813,7 @@ Java::
 +
 [source,java,indent=0,subs="verbatim,quotes"]
 ----
-    Resource location = new FileSystemResource("public-resources/");
+    Resource location = new FileUrlResource("public-resources/");
     RouterFunction<ServerResponse> resources = RouterFunctions.resources("/resources/**", location);
 ----
 
@@ -821,7 +821,7 @@ Kotlin::
 +
 [source,kotlin,indent=0,subs="verbatim,quotes"]
 ----
-    val location = FileSystemResource("public-resources/")
+    val location = FileUrlResource("public-resources/")
     val resources = router { resources("/resources/**", location) }
 ----
 ======

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/RouterFunctions.java

@@ -184,7 +184,7 @@ public abstract class RouterFunctions {
 	 * Route requests that match the given pattern to resources relative to the given root location.
 	 * For instance
 	 * <pre class="code">
-	 * Resource location = new FileSystemResource("public-resources/");
+	 * Resource location = new FileUrlResource("public-resources/");
 	 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resources("/resources/**", location);
      * </pre>
 	 * @param pattern the pattern to match
@@ -201,7 +201,7 @@ public abstract class RouterFunctions {
 	 * Route requests that match the given pattern to resources relative to the given root location.
 	 * For instance
 	 * <pre class="code">
-	 * Resource location = new FileSystemResource("public-resources/");
+	 * Resource location = new FileUrlResource("public-resources/");
 	 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resources("/resources/**", location);
      * </pre>
 	 * @param pattern the pattern to match
@@ -224,7 +224,7 @@ public abstract class RouterFunctions {
 	 * <pre class="code">
 	 * Mono&lt;Resource&gt; defaultResource = Mono.just(new ClassPathResource("index.html"));
 	 * Function&lt;ServerRequest, Mono&lt;Resource&gt;&gt; lookupFunction =
-	 *   RouterFunctions.resourceLookupFunction("/resources/**", new FileSystemResource("public-resources/"))
+	 *   RouterFunctions.resourceLookupFunction("/resources/**", new FileUrlResource("public-resources/"))
 	 *     .andThen(resourceMono -&gt; resourceMono.switchIfEmpty(defaultResource));
 	 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resources(lookupFunction);
      * </pre>
@@ -761,7 +761,7 @@ public abstract class RouterFunctions {
 		 * Route requests that match the given pattern to resources relative to the given root location.
 		 * For instance
 		 * <pre class="code">
-		 * Resource location = new FileSystemResource("public-resources/");
+		 * Resource location = new FileUrlResource("public-resources/");
 		 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resources("/resources/**", location);
 	     * </pre>
 		 * @param pattern the pattern to match
@@ -775,7 +775,7 @@ public abstract class RouterFunctions {
 		 * Route requests that match the given pattern to resources relative to the given root location.
 		 * For instance
 		 * <pre class="code">
-		 * Resource location = new FileSystemResource("public-resources/");
+		 * Resource location = new FileUrlResource("public-resources/");
 		 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resources("/resources/**", location);
 	     * </pre>
 		 * @param pattern the pattern to match

spring-webmvc/src/main/java/org/springframework/web/servlet/function/RouterFunctions.java

@@ -168,7 +168,7 @@ public abstract class RouterFunctions {
 	 * Route requests that match the given pattern to resources relative to the given root location.
 	 * For instance
 	 * <pre class="code">
-	 * Resource location = new FileSystemResource("public-resources/");
+	 * Resource location = new FileUrlResource("public-resources/");
 	 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resources("/resources/**", location);
      * </pre>
 	 * @param pattern the pattern to match
@@ -185,7 +185,7 @@ public abstract class RouterFunctions {
 	 * Route requests that match the given pattern to resources relative to the given root location.
 	 * For instance
 	 * <pre class="code">
-	 * Resource location = new FileSystemResource("public-resources/");
+	 * Resource location = new FileUrlResource("public-resources/");
 	 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resources("/resources/**", location);
      * </pre>
 	 * @param pattern the pattern to match
@@ -209,7 +209,7 @@ public abstract class RouterFunctions {
 	 * <pre class="code">
 	 * Optional&lt;Resource&gt; defaultResource = Optional.of(new ClassPathResource("index.html"));
 	 * Function&lt;ServerRequest, Optional&lt;Resource&gt;&gt; lookupFunction =
-	 *   RouterFunctions.resourceLookupFunction("/resources/**", new FileSystemResource("public-resources/"))
+	 *   RouterFunctions.resourceLookupFunction("/resources/**", new FileUrlResource("public-resources/"))
 	 *     .andThen(resource -&gt; resource.or(() -&gt; defaultResource));
 	 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resources(lookupFunction);
      * </pre>
@@ -674,7 +674,7 @@ public abstract class RouterFunctions {
 		 * Route requests that match the given pattern to resources relative to the given root location.
 		 * For instance
 		 * <pre class="code">
-		 * Resource location = new FileSystemResource("public-resources/");
+		 * Resource location = new FileUrlResource("public-resources/");
 		 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resources("/resources/**", location);
 	     * </pre>
 		 * @param pattern the pattern to match
@@ -688,7 +688,7 @@ public abstract class RouterFunctions {
 		 * Route requests that match the given pattern to resources relative to the given root location.
 		 * For instance
 		 * <pre class="code">
-		 * Resource location = new FileSystemResource("public-resources/");
+		 * Resource location = new FileUrlResource("public-resources/");
 		 * RouterFunction&lt;ServerResponse&gt; resources = RouterFunctions.resources("/resources/**", location);
 	     * </pre>
 		 * @param pattern the pattern to match