Add Copilot Usage Summary for Organization

[claystation]

Github has a Rest API to get the usage summary of Copilot within the organization. This PR implements the functionality to fetch that data.
API Docs: Here

Please let me know what you think!

(Fixup of #3318 due to CLA signing issues)

[claystation]

I will implement other missing API methods as well, converting to draft for now whilst i work on more!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.33%. Comparing base (2b8c7fa) to head (8b04d1c).
Report is 151 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3321      +/-   ##
==========================================
- Coverage   97.72%   93.33%   -4.39%     
==========================================
  Files         153      171      +18     
  Lines       13390    11795    -1595     
==========================================
- Hits        13085    11009    -2076     
- Misses        215      692     +477     
- Partials       90       94       +4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[claystation]

@gmlewis i added all missing API methods from the Github API :) Let me know what you think!

[gmlewis]

Thank you, @claystation !
A couple minor tweaks, please, and one question.

After that, we should be ready for a second LGTM+Approval from any other contributor to this repo before merging.

[gmlewis]

Also, please run go generate ./... as discussed in step 4 of CONTRIBUTING.md and push (not force-push) the changes to this PR. Thanks!

[gmlewis]

Thank you, @claystation !
LGTM.

Awaiting second LGTM+Approval from any other contributor to this repo before merging.

[tomfeigin]

LGTM

[gmlewis]

Thank you, @tomfeigin !
Merging.