feat(static-file): replace string metric name with enum

[9547]

close #8758

FYI, this PR also changed the reth_static_files_xxx metric names(from label to name):

-reth_static_files_jar_provider_calls_total{segment="headers",operation="prune"}  0
+reth_static_files_jar_provider_headers_prune_total 0

BTW, I'm not quite satisfied with the 18 match arms(match (segment, operation)), don't know if there are any other solutions.

[Rjected]

BTW, I'm not quite satisfied with the 18 match arms(match (segment, operation)), don't know if there are any other solutions.

Might be a good idea to have separate metrics structs for each segment, and separate methods for each segment which handle the recording for each provider operation.

[kamuik16]

Hey! This will be conflicting with #8718. should prob merge that one first?

[mattsse]

ah okay, this basically flattens the map and adds dedicated metrics for all variants

I this this is better because now it's visible what metrics we have, the match isn't that bad

ptal @joshieDo @shekhirin

[Rjected]

After some discussion with @shekhirin we actually decided to go with a different approach than the initial issue entirely. The underlying problem with the use of labels right now is that it somewhat obscures how to go from a metric name in grafana, to where the metric is actually set in the codebase.

With MakeCanonicalMetrics, the issue was that the graphs were poorly implemented and would need to be revised as well, whereas here that is not the case.

I think the best approach would be to add descriptions to each metric that uses labels, indicating where in the code to find that metric, rather than removing labels from the codebase.

Labels for this type of thing are best practices w.r.t prometheus naming:
https://prometheus.io/docs/practices/naming/

Thank you for your effort though @9547!