metrics(indexer): Add metrics around join time for chained processing strategies

[ayirr7]

Currently, we have a total shutdown time for the indexer; however, we don't have a better breakdown to understand which strategies make up this shutdown time and how much.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 79.72%. Comparing base (910ff45) to head (723e323). Report is 1268 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #68828   +/-   ##
=======================================
  Coverage   79.72%   79.72%           
=======================================
  Files        6420     6422    +2     
  Lines      284558   284641   +83     
  Branches    49022    49039   +17     
=======================================
+ Hits       226868   226940   +72     
- Misses      57324    57335   +11     
  Partials      366      366           

Files	Coverage Δ
.../sentry/sentry_metrics/consumers/indexer/common.py	95.87% <100.00%> (+0.04%)	:arrow_up:
...entry/sentry_metrics/consumers/indexer/parallel.py	81.72% <100.00%> (+0.60%)	:arrow_up:

... and 19 files with indirect coverage changes

[getsantry[bot]]

This pull request has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you add the label WIP, I will leave it alone unless WIP is removed ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀