feat!: rename metrics and service

[Kavindu-Dodan]

This PR

Fixes #712

Refer the following table for metrics renames and their units,

Old	New	Unit
http_request_duration_seconds	http.server.duration	s
http_response_size_bytes	http.server.response.size	By
http_requests_inflight	http.server.active_requests	{request}
impressions	feature_flag.flagd.impression	{impression}
reasons	feature_flag.flagd.evaluation.reason	{reason}

Validation

This change was validated against an OTel setup. Consider following screen captures,

[codecov]

Codecov Report

Merging #730 (ee76343) into main (3f263c6) will increase coverage by 0.04%.
The diff coverage is 100.00%.

❗ Current head ee76343 differs from pull request most recent head f2f9465. Consider uploading reports for the commit f2f9465 to get more accurate results

@@            Coverage Diff             @@
##             main     #730      +/-   ##
==========================================
+ Coverage   73.68%   73.72%   +0.04%     
==========================================
  Files          26       26              
  Lines        2603     2607       +4     
==========================================
+ Hits         1918     1922       +4     
  Misses        612      612              
  Partials       73       73              

Impacted Files	Coverage Δ
core/pkg/runtime/from_config.go	60.78% <ø> (ø)
core/pkg/telemetry/metrics.go	100.00% <100.00%> (ø)

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