[MM-55268] Implement ServeMetrics plugins hook (#24249)

* Implement ServeMetrics plugins hook

* Update error id

* Simplify

* Revert "Simplify"

This reverts commit c9dc5d5eac6c933ff69e158cf3e34d0973bd3bcd.

* Add comment and error handler

* Wrap error

* Update translation file

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Co-authored-by: Mattermost Build <build@mattermost.com>

server/i18n/en.json

@@ -6306,6 +6306,10 @@
     "id": "app.plugin.store_signature.app_error",
     "translation": "Unable to store the plugin signature to the configured file store."
   },
+  {
+    "id": "app.plugin.subpath_parse.app_error",
+    "translation": "Failed to parse SiteURL subpath"
+  },
   {
     "id": "app.plugin.sync.list_filestore.app_error",
     "translation": "Error reading files from the plugins folder in the file store."