Add v2 endpoints for RUM custom metrics. (#1877)

Co-authored-by: ci.datadog-api-spec <packages@datadoghq.com>

Author: api-clients-generation-pipeline[bot]

.apigentools-info

@@ -4,13 +4,13 @@
     "spec_versions": {
         "v1": {
             "apigentools_version": "1.6.6",
-            "regenerated": "2024-10-30 18:58:11.764801",
-            "spec_repo_commit": "755120dd"
+            "regenerated": "2024-10-31 14:19:56.991956",
+            "spec_repo_commit": "47da2e01"
         },
         "v2": {
             "apigentools_version": "1.6.6",
-            "regenerated": "2024-10-30 18:58:11.783283",
-            "spec_repo_commit": "755120dd"
+            "regenerated": "2024-10-31 14:19:57.012102",
+            "spec_repo_commit": "47da2e01"
         }
     }
 }