chore(hybridcloud) Remove rpcmetrics module

[markstory]

This was added early into our RPC service build out as a way to find endpoints that had many RPC operations. Unfortunately span attributes cannot be queried so there is no useful way to get to this data.

Not having this data is a simpler design than having it. We can use other metrics to track RPC throughput and latency.

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: src/sentry/api/base.py

Function	Unhandled Issue
dispatch	AssertionError: Expected a Response, HttpResponse or StreamingHttpResponse to be returned from the view, bu... ... Event Count: 9

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.01%. Comparing base (deb83df) to head (8a10dc2).
Report is 14 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #73319      +/-   ##
==========================================
- Coverage   78.02%   78.01%   -0.01%     
==========================================
  Files        6632     6631       -1     
  Lines      296026   295957      -69     
  Branches    50985    50970      -15     
==========================================
- Hits       230963   230887      -76     
- Misses      58783    58788       +5     
- Partials     6280     6282       +2     

Files	Coverage Δ
src/sentry/api/base.py	91.28% <100.00%> (-0.05%)	⬇️
src/sentry/hybridcloud/rpc/service.py	86.11% <100.00%> (-0.09%)	⬇️

... and 3 files with indirect coverage changes

[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ ValueError: invalid literal for int() with base 10: 'threat-log' /api/0/organizations/{organization_id_or_slug}/... View Issue
• ‼️ SnubaError: HTTPConnectionPool(host='127.0.0.1', port=10006): Read timed out. (read timeout=30) /api/0/organizations/{organization_id_or_slug}/... View Issue
• ‼️ InvalidResponse: Too Many Requests /api/0/projects/{organization_id_or_slug}/{proj... View Issue
• ‼️ JSONDecodeError: unexpected character: line 1 column 1 (char 0) /extensions/slack/action/ View Issue
• ‼️ OverflowError: date value out of range /api/0/projects/{organization_id_or_slug}/{proj... View Issue

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