Service Accounts - adjust fleet-server privileges for synthetics (#71799)

This PR adds a new index pattern to "synthetics-*" to fleet-server's privilege
set along with "metrics-" and "traces-*".

x-pack/plugin/security/qa/service-account/src/javaRestTest/java/org/elasticsearch/xpack/security/authc/service/ServiceAccountIT.java

@@ -79,6 +79,7 @@ public class ServiceAccountIT extends ESRestTestCase {
         + "            \"logs-*\",\n"
         + "            \"metrics-*\",\n"
         + "            \"traces-*\",\n"
+        + "            \"synthetics-*\",\n"
         + "            \".logs-endpoint.diagnostic.collection-*\"\n"
         + "          ],\n"
         + "          \"privileges\": [\n"

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/service/ElasticServiceAccounts.java

@@ -28,7 +28,7 @@ final class ElasticServiceAccounts {
             new RoleDescriptor.IndicesPrivileges[]{
                 RoleDescriptor.IndicesPrivileges
                     .builder()
-                    .indices("logs-*", "metrics-*", "traces-*", ".logs-endpoint.diagnostic.collection-*")
+                    .indices("logs-*", "metrics-*", "traces-*", "synthetics-*", ".logs-endpoint.diagnostic.collection-*")
                     .privileges("write", "create_index", "auto_configure")
                     .build(),
                 RoleDescriptor.IndicesPrivileges

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/service/ElasticServiceAccountsTests.java

@@ -62,6 +62,7 @@ public class ElasticServiceAccountsTests extends ESTestCase {
             "logs-" + randomAlphaOfLengthBetween(1, 20),
             "metrics-" + randomAlphaOfLengthBetween(1, 20),
             "traces-" + randomAlphaOfLengthBetween(1, 20),
+            "synthetics-" + randomAlphaOfLengthBetween(1, 20),
             ".logs-endpoint.diagnostic.collection-" + randomAlphaOfLengthBetween(1, 20))
             .stream().map(this::mockIndexAbstraction)
             .forEach(index -> {