[anza migration] replace binaries backend

[yihau]

Summary of Changes

• remove S3 and use GCS as binaries backend
• point things to Anza URL

Before Merge

• setup GCS_RELEASE_BUCKET_WRITER_CREDIENTIAL for Github Actions
• setup GCS_RELEASE_BUCKET_WRITER_CREDIENTIAL for the release agent in Buildkite

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

❗ No coverage uploaded for pull request base (master@28a320d). Click here to learn what that means.

Additional details and impacted files

@@            Coverage Diff            @@
##             master       #6   +/-   ##
=========================================
  Coverage          ?    81.6%           
=========================================
  Files             ?      832           
  Lines             ?   224856           
  Branches          ?        0           
=========================================
  Hits              ?   183532           
  Misses            ?    41324           
  Partials          ?        0           

[mergify]

Backports to the stable branch are to be avoided unless absolutely necessary for fixing bugs, security issues, and perf regressions. Changes intended for backport should be structured such that a minimum effective diff can be committed separately from any refactoring, plumbing, cleanup, etc that are not strictly necessary to achieve the goal. Any of the latter should go only into master and ride the normal stabilization schedule.

[mergify]

Backports to the beta branch are to be avoided unless absolutely necessary for fixing bugs, security issues, and perf regressions. Changes intended for backport should be structured such that a minimum effective diff can be committed separately from any refactoring, plumbing, cleanup, etc that are not strictly necessary to achieve the goal. Any of the latter should go only into master and ride the normal stabilization schedule. Exceptions include CI/metrics changes, CLI improvements and documentation updates on a case by case basis.