🌱 Add support for commit-based lookup to GitHub APIs

[azeemshaikh38]

• Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• PR title follows the guidelines defined in https://github.com/ossf/scorecard/blob/main/CONTRIBUTING.md#pr-process

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  Add support for non-HEAD commit lookup in GitHub RepoClient. This PR attempts to add the support while not changing the behavior. Once the e2e tests confirm that this does not break anything will follow-up with exposing this feature externally.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  No.

[naveensrinivasan]

Nice! Thanks

[github-actions]

Integration tests success for
[384d59e]
(https://github.com/ossf/scorecard/actions/runs/1808898824)

[github-actions]

Integration tests success for
[f83c1fd]
(https://github.com/ossf/scorecard/actions/runs/1808927452)

[codecov-commenter]

Codecov Report

Merging #1612 (f83c1fd) into main (30fc06e) will decrease coverage by 0.12%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #1612      +/-   ##
==========================================
- Coverage   54.72%   54.60%   -0.13%     
==========================================
  Files          72       72              
  Lines        6257     6271      +14     
==========================================
  Hits         3424     3424              
- Misses       2612     2626      +14     
  Partials      221      221              

[github-actions]

Integration tests success for
[2e3877f]
(https://github.com/ossf/scorecard/actions/runs/1809024005)