Optimize StringUtils.cleanPath

Add an early exit to `StringUtils.cleanPath` to save array creating and
string concatenation. With a typical Spring application, the `cleanPath`
method can be called over 600 times, often with a path constructed by
a `ClassPathResource` that is likely to already be clean.

Closes gh-22568

spring-core/src/main/java/org/springframework/util/StringUtils.java

@@ -639,6 +639,11 @@ public abstract class StringUtils {
 		}
 		String pathToUse = replace(path, WINDOWS_FOLDER_SEPARATOR, FOLDER_SEPARATOR);
 
+		// Shortcut if there is no work to do
+		if (pathToUse.indexOf('.') == -1) {
+			return pathToUse;
+		}
+
 		// Strip prefix from path to analyze, to not treat it as part of the
 		// first path element. This is necessary to correctly parse paths like
 		// "file:core/../core/io/Resource.class", where the ".." should just