Enable customizing REST tests blacklist (#31074)

This commit enables adding additional REST tests to the blacklist for
builds that already define tests.rest.blacklist.

test/framework/src/main/java/org/elasticsearch/test/rest/yaml/ESClientYamlSuiteTestCase.java

@@ -69,6 +69,11 @@ public abstract class ESClientYamlSuiteTestCase extends ESRestTestCase {
      * e.g. "-Dtests.rest.blacklist=get/10_basic/*"
      */
     public static final String REST_TESTS_BLACKLIST = "tests.rest.blacklist";
+    /**
+     * We use tests.rest.blacklist in build files to blacklist tests; this property enables a user to add additional blacklisted tests on
+     * top of the tests blacklisted in the build.
+     */
+    public static final String REST_TESTS_BLACKLIST_ADDITIONS = "tests.rest.blacklist_additions";
     /**
      * Property that allows to control whether spec validation is enabled or not (default true).
      */
@@ -125,6 +130,10 @@ public abstract class ESClientYamlSuiteTestCase extends ESRestTestCase {
             for (final String entry : blacklist) {
                 blacklistPathMatchers.add(new BlacklistedPathPatternMatcher(entry));
             }
+            final String[] blacklistAdditions = resolvePathsProperty(REST_TESTS_BLACKLIST_ADDITIONS, null);
+            for (final String entry : blacklistAdditions) {
+                blacklistPathMatchers.add(new BlacklistedPathPatternMatcher(entry));
+            }
         }
         assert restTestExecutionContext != null;
         assert adminExecutionContext != null;