feat: Add "K_REVISION" to environment variable release check (exposed by cloud run)

[rpradal]

Description

Google cloud run exposes K_REVISION env varibale to keep track of revisions. This can be a good candidate for sentry release.
Today it already works for Google app engine via GAE_DEPLOYMENT_ID

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.27%. Comparing base (2ce4379) to head (c5a983c).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5222      +/-   ##
==========================================
+ Coverage   84.25%   84.27%   +0.01%     
==========================================
  Files         181      182       +1     
  Lines       18463    18508      +45     
  Branches     3288     3288              
==========================================
+ Hits        15556    15597      +41     
- Misses       1894     1905      +11     
+ Partials     1013     1006       -7     

Files with missing lines	Coverage Δ
sentry_sdk/utils.py	86.37% <ø> (ø)

... and 2 files with indirect coverage changes

[alexander-alderman-webb]

Thanks for the contribution @rpradal