[gh release create] Fail when there are no new commits since the last release

[iamazeem]

Fixes #6059.

Introduce a new Boolean flag --only-new (--fail-on-no-commits) to create release only if new commits exist since the last release.
Only the latest published release is checked. The draft and pre-release releases are excluded.

APIs Used

• Get the latest release /repos/{owner}/{repo}/releases/latest
• Compare two commits /repos/{owner}/{repo}/compare/{basehead}

Tests Cases

1. New commits exist but no published release exists - release created (exit code 0)
2. New commits exist and the last release exists too - release created (exit code 0)
3. No new commits exist but the last release exists - release not created (exit code 1)

Test Runs

# Test cases 1 and 2
$ bin/gh release create --repo iamazeem/test --fail-on-no-commits --generate-notes v1.2.3
https://github.com/iamazeem/test/releases/tag/v1.2.3

# Test case 3 (exit code 1)
$ bin/gh release create --repo iamazeem/test `--fail-on-no-commits` --generate-notes v1.2.3
no new commits since the last release

---

UPDATE

During review discussions, the flag has been renamed to --fail-on-no-commits.

[williammartin]

Lots of good stuff in this PR thank you. Couple of notes.

[williammartin]

One minor error change, and then I'm happy to ship this, thanks.

[williammartin]

Looks great to me thanks!