fix: path metric labels (#6400) (#6518)

## About the changes
Some of our metrics are not labeled correctly, one example is
`<base-path>/api/frontend/client/metrics` is labeled as
`/client/metrics`. We can see that in internal-backstage/prometheus:


![image](https://github.com/Unleash/unleash/assets/455064/0d8f1f40-8b5b-49d4-8a88-70b523e9be09)

This issue affects all endpoints that fail to validate the request body.
Also, endpoints that are rejected by the authorization-middleware or the
api-token-middleware are reported as `(hidden)`.

To gain more insights on our api usage but being protective of metrics
cardinality we're prefixing `(hidden)` with some well known base urls:
https://github.com/Unleash/unleash/pull/6400/files#diff-1ed998ca46ffc97c9c0d5d400bfd982dbffdb3004b78a230a8a38e7644eee9b6R17-R33

## How to reproduce:
Make an invalid call to metrics (e.g. stop set to null), then check
/internal-backstage/prometheus and find the 400 error. Expected to be at
`path="/api/client/metrics"` but will have `path=""`:
```shell
curl -H"Authorization: *:development.unleash-insecure-client-api-token" -H'Content-type: application/json' localhost:4242/api/client/metrics -d '{
  "appName": "bash-test",
  "instanceId": "application-name-dacb1234",
  "environment": "development",
  "bucket": {
    "start": "2023-07-27T11:23:44Z",
    "stop": null,
    "toggles": {
      "myCoolToggle": {
        "yes": 25,
        "no": 42,
        "variants": {
          "blue": 6,
          "green": 15,
          "red": 46
        }
      },
      "myOtherToggle": {
        "yes": 0,
        "no": 100
      }
    }
  }
}'
```

<!-- Thanks for creating a PR! To make it easier for reviewers and
everyone else to understand what your changes relate to, please add some
relevant content to the headings below. Feel free to ignore or delete
sections that you don't think are relevant. Thank you! ❤️ -->

## About the changes
<!-- Describe the changes introduced. What are they and why are they
being introduced? Feel free to also add screenshots or steps to view the
changes if they're visual. -->

<!-- Does it close an issue? Multiple? -->
Closes #

<!-- (For internal contributors): Does it relate to an issue on public
roadmap? -->
<!--
Relates to [roadmap](https://github.com/orgs/Unleash/projects/10) item:
#
-->

### Important files
<!-- PRs can contain a lot of changes, but not all changes are equally
important. Where should a reviewer start looking to get an overview of
the changes? Are any files particularly important? -->


## Discussion points
<!-- Anything about the PR you'd like to discuss before it gets merged?
Got any questions or doubts? -->

src/lib/__snapshots__/create-config.test.ts.snap

@@ -132,6 +132,7 @@ exports[`should create default config 1`] = `
       "personalAccessTokensKillSwitch": false,
       "proPlanAutoCharge": false,
       "queryMissingTokens": false,
+      "responseTimeMetricsFix": false,
       "responseTimeWithAppNameKillSwitch": false,
       "scimApi": false,
       "sdkReporting": false,