Adds new rekor metrics for latency and QPS.

[var-sdk]

The current server metrics have two problems:

1. They don't capture method so we can't differentiate POST vs GET/write vs read.
2. They use the path as passed by the caller for the path field. This prevents us from aggregating correctly ("api/v1/log" is a different time series than "api/v1/log/") and can be a scale risk as it lets end users create new time series arbitrarily.

The two new metrics track latency by endpoint/method, and qps by endpoint/method/status code for error budget. The old metrics will be removed once monitoring has been updated to use the new metrics.

Summary

Release Note

Documentation

[codecov-commenter]

Codecov Report

Merging #1059 (7e900ed) into main (8260a79) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1059   +/-   ##
=======================================
  Coverage   41.02%   41.02%           
=======================================
  Files          71       71           
  Lines        7061     7061           
=======================================
  Hits         2897     2897           
  Misses       3858     3858           
  Partials      306      306           

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[bobcallaway]

lgtm, thanks for doing this!