Make ESRestTestCase client configuration more configurable in subclas…

…ses (elastic#96987)

We want to be able to tweak client configuration in tests extending
ESRestTestCase. This makes that simpler by allowing overriding the
general client configuration.

qa/ccs-common-rest/src/yamlRestTest/java/org/elasticsearch/test/rest/yaml/RcsCcsCommonYamlTestSuiteIT.java

@@ -142,7 +142,7 @@ private static Map<String, Object> createCrossClusterAccessApiKey() throws IOExc
         final int portSeparator = url.lastIndexOf(':');
         final var httpHost = new HttpHost(url.substring(0, portSeparator), Integer.parseInt(url.substring(portSeparator + 1)), "http");
         RestClientBuilder builder = RestClient.builder(httpHost);
-        configureClient(builder, Settings.EMPTY);
+        doConfigureClient(builder, Settings.EMPTY);
         builder.setStrictDeprecationMode(true);
         try (RestClient fulfillingClusterClient = builder.build()) {
             final Response createApiKeyResponse = fulfillingClusterClient.performRequest(createApiKeyRequest);

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

@@ -1302,7 +1302,14 @@ protected RestClient buildClient(Settings settings, HttpHost[] hosts) throws IOE
         return builder.build();
     }
 
-    protected static void configureClient(RestClientBuilder builder, Settings settings) throws IOException {
+    /**
+     * Override this to configure the client with additional settings.
+     */
+    protected void configureClient(RestClientBuilder builder, Settings settings) throws IOException {
+        doConfigureClient(builder, settings);
+    }
+
+    protected static void doConfigureClient(RestClientBuilder builder, Settings settings) throws IOException {
         String truststorePath = settings.get(TRUSTSTORE_PATH);
         String certificateAuthorities = settings.get(CERTIFICATE_AUTHORITIES);
         String clientCertificatePath = settings.get(CLIENT_CERT_PATH);

x-pack/plugin/eql/qa/common/src/main/java/org/elasticsearch/test/eql/RemoteClusterAwareEqlRestTestCase.java

@@ -68,7 +68,7 @@ protected static RestHighLevelClient highLevelClient(RestClient client) {
 
     protected static RestClient clientBuilder(Settings settings, HttpHost[] hosts) throws IOException {
         RestClientBuilder builder = RestClient.builder(hosts);
-        configureClient(builder, settings);
+        doConfigureClient(builder, settings);
 
         int timeout = Math.toIntExact(timeout().millis());
         builder.setRequestConfigCallback(

x-pack/plugin/security/qa/multi-cluster/src/javaRestTest/java/org/elasticsearch/xpack/remotecluster/AbstractRemoteClusterSecurityTestCase.java

@@ -94,7 +94,7 @@ static RestClient buildRestClient(ElasticsearchCluster targetCluster) {
         final var httpHost = new HttpHost(url.substring(0, portSeparator), Integer.parseInt(url.substring(portSeparator + 1)), "http");
         RestClientBuilder builder = RestClient.builder(httpHost);
         try {
-            configureClient(builder, Settings.EMPTY);
+            doConfigureClient(builder, Settings.EMPTY);
         } catch (IOException e) {
             throw new UncheckedIOException(e);
         }

x-pack/plugin/sql/qa/server/src/main/java/org/elasticsearch/xpack/sql/qa/rest/RemoteClusterAwareSqlRestTestCase.java

@@ -61,7 +61,7 @@ public static void closeRemoteClients() throws IOException {
 
     protected static RestClient clientBuilder(Settings settings, HttpHost[] hosts) throws IOException {
         RestClientBuilder builder = RestClient.builder(hosts);
-        configureClient(builder, settings);
+        doConfigureClient(builder, settings);
 
         int timeout = Math.toIntExact(timeout().millis());
         builder.setRequestConfigCallback(