Fix metrics logging of http_error_count (#16055)

**What type of PR is this?**

Bug fix

**What does this PR do? Why is it needed?**

I am seeing massive metrics cardinality on error cases. 

Example:

```
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682952",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682953",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682954",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682955",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682956",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682957",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682958",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682959",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682960",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682961",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682962",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682966",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682967",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682968",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682969",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682970",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682971",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682972",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682973",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682974",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682975",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682976",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682977",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682978",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682980",method="GET"} 2
http_error_count{code="Not Found",endpoint="/eth/v1/beacon/blob_sidecars/1682983",method="GET"} 2
```

Now it looks like this:

```
# TYPE http_error_count counter
http_error_count{code="Not Found",endpoint="beacon.GetBlockV2",method="GET"} 606
http_error_count{code="Not Found",endpoint="blob.Blobs",method="GET"} 4304
```

**Which issues(s) does this PR fix?**

**Other notes for review**


Other uses of http metrics use the endpoint name rather than the request
URL.

**Acknowledgements**

- [x] I have read
[CONTRIBUTING.md](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md).
- [x] I have included a uniquely named [changelog fragment
file](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md#maintaining-changelogmd).
- [x] I have added a description to this PR with sufficient context for
reviewers to understand this PR.

Author: prestonvanloon

beacon-chain/rpc/endpoints.go

@@ -73,7 +73,7 @@ func (e *endpoint) handlerWithMiddleware() http.HandlerFunc {
 		handler.ServeHTTP(rw, r)
 
 		if rw.statusCode >= 400 {
-			httpErrorCount.WithLabelValues(r.URL.Path, http.StatusText(rw.statusCode), r.Method).Inc()
+			httpErrorCount.WithLabelValues(e.name, http.StatusText(rw.statusCode), r.Method).Inc()
 		}
 	}
 }

changelog/pvl-metrics-fix.md

@@ -0,0 +1,3 @@
+### Fixed
+
+- http_error_count now matches the other cases by listing the endpoint name rather than the actual URL requested. This improves metrics cardinality.