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.