feat: add breadcrumb ringbuffer to avoid O(n) memmove

[JoshuaMoelans]

Fixes #1006

(in progress)

• Creating ringbuffer
• Storing items to ringbuffer
• Rethink decref test -> add a test that checks reference counts of objects added/overwritten in ringbuffer
• Extracting items from ringbuffer (by converting back to regular list)
• Updating docs
• Updating changelog

[github-actions]

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by 🚫 dangerJS against 190a4a5

[codecov]

Codecov Report

Attention: Patch coverage is 83.78378% with 6 lines in your changes missing coverage. Please review.

Project coverage is 82.60%. Comparing base (b598af0) to head (190a4a5).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1060      +/-   ##
==========================================
- Coverage   82.63%   82.60%   -0.04%     
==========================================
  Files          53       53              
  Lines        7660     7680      +20     
  Branches     1208     1209       +1     
==========================================
+ Hits         6330     6344      +14     
- Misses       1216     1224       +8     
+ Partials      114      112       -2     

[supervacuus]

This looks great; we can merge it with minor finishing touches.