Add pagination support to GetIdpGroupId method

[ArinGhazarian]

The GetIdpGroupId method hasn't been using pagination to get all groups so far. This PR adds pagination support to the GetIdpGroupId method by using the new GetAllAsync overload that accepts a result collection selector.

The new overload was necessary because the List extrernal groups API is returning a Json object instead of an Array. With the new selector it'd be now possible to specify the desired field which is the result collection.

• [x] Did you write/update appropriate tests
• [x] Release notes updated (if appropriate)
• [x] Appropriate logging output
• [x] Issue linked
• [x] Docs updated (or issue created)
• [x] New package licenses are added to ThirdPartyNotices.txt (if applicable)

[github-actions[bot]]

Unit Test Results

811 tests   811 :white_check_mark:  21s :stopwatch:   1 suites    0 :zzz:   1 files      0 :x:

Results for commit a20fabdc.

[github-actions[bot]]

Package	Line Rate	Branch Rate	Complexity	Health
bbs2gh	78%	73%	651	✔
ado2gh	84%	78%	627	✔
Octoshift	87%	76%	1276	✔
gei	79%	70%	519	✔
Summary	83% (6824 / 8177)	75% (1535 / 2046)	3073	✔

[ArinGhazarian]

Closing in favor of https://github.com/github/gh-gei/pull/1267, the changes of this branch were merged into it.