Block use of current version feature in yaml tests (#112737)

Using the current version as a condition is not compatible with Serverless, as the version doesn't change between commits. Cluster features should be used instead.

test/framework/src/main/java/org/elasticsearch/test/rest/ESRestTestFeatureService.java

@@ -95,6 +95,27 @@ class ESRestTestFeatureService implements TestFeatureService {
         Matcher matcher = VERSION_FEATURE_PATTERN.matcher(featureId);
         if (matcher.matches()) {
             Version extractedVersion = Version.fromString(matcher.group(1));
+            if (extractedVersion.after(Version.CURRENT)) {
+                throw new IllegalArgumentException(
+                    Strings.format(
+                        "Cannot use a synthetic feature [%s] for a version after the current version [%s]",
+                        featureId,
+                        Version.CURRENT
+                    )
+                );
+            }
+
+            if (extractedVersion.equals(Version.CURRENT)) {
+                throw new IllegalArgumentException(
+                    Strings.format(
+                        "Cannot use a synthetic feature [%s] for the current version [%s]; "
+                            + "please define a test cluster feature alongside the corresponding code change instead",
+                        featureId,
+                        Version.CURRENT
+                    )
+                );
+            }
+
             return checkCollection(nodeVersions, v -> v.onOrAfter(extractedVersion), any);
         }