fix: Prevent unnecessary retries when checking repository existence b…

[AakashSuresh2003]

…y updating GetNonSuccessAsync to retry only on transient 5xx errors, skip deterministic statuses (200/404/301/4xx), add full test coverage, and ensure DoesRepoExist makes a single API call for expected responses. (#1447)

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

[github-actions[bot]]

Unit Test Results

  1 files    1 suites   10m 25s ⏱️ 975 tests 975 ✅ 0 💤 0 ❌ 976 runs  976 ✅ 0 💤 0 ❌

Results for commit abd14ab7.

:recycle: This comment has been updated with latest results.

[github-actions[bot]]

Package	Line Rate	Branch Rate	Complexity	Health
ado2gh	72%	70%	718	➖
Octoshift	83%	73%	1749	✔
bbs2gh	83%	78%	663	✔
gei	80%	71%	574	✔
Summary	81% (7762 / 9641)	73% (1847 / 2533)	3704	✔

[brianaj]

closing in favor of https://github.com/github/gh-gei/pull/1487

[brianaj]

@AakashSuresh2003 I am going to hold off on shipping this, I have some concerns with this failing fast for 429s and possible other non-5** that we should retry.