Remove unused Gerrit and BoringSSL Bot configuration

[andrewhop]

Description of changes:

AWS-LC does not use Gerrit or the Google build server and doesn't need any of this configuration.

Call-outs:

I quickly skimmed these files and didn't find anything useful that we would want to use/keep.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.75%. Comparing base (4924695) to head (e6d8bf8).
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2316      +/-   ##
==========================================
+ Coverage   78.73%   78.75%   +0.01%     
==========================================
  Files         616      620       +4     
  Lines      107589   107936     +347     
  Branches    15285    15333      +48     
==========================================
+ Hits        84712    85001     +289     
- Misses      22223    22278      +55     
- Partials      654      657       +3     

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[skmcgrail]

Sanitize job is failing, as it seems to rely on this: https://github.com/aws/aws-lc/blob/main/CMakeLists.txt#L900-L910