Implement GH Check Caching

[trent-codecov]

Research: https://github.com/codecov/worker-archive/issues/1205

We needlessly update GH checks many times.

Please implement caching scheme to cache last update and avoid sending sequential duplicates.

High level pseudocode to use as at least some inspiration

new_patch_val = 'the new patch value'
cache_val = get_cache(patch_id)
if cache_val && cache_val == new_patch_val
  put_cache(patch_id, new_patch_val, SOME_EXPIRATION)
else
  put_cache(patch_id, new_patch_val, SOME_EXPIRATION)
  send_github_check(patch_id, new_patch_val)