feat(metricprovider): Add Google Managed Prometheus auth

[LiorFriedmanYahoo]

Hi community, we're Noy and Lior from the Kubernetes team at Yahoo. We're using Argo Rollouts with Google Managed Prometheus and want to contribute our work to the project.

Fixes #3307.

We refrained from adding tests because the change is very minimal, and it's difficult to test without bringing up a GMP instance. We did test this authentication method on our infrastructure.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional with a list of types and scopes found here, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed my commits with DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My builds are green. Try syncing with master if they are not.
• My organization is added to USERS.md.

[github-actions]

Published E2E Test Results

  4 files    4 suites   4h 11m 16s ⏱️
117 tests 105 ✅  7 💤  5 ❌
500 runs  438 ✅ 28 💤 34 ❌

For more details on these failures, see this check.

Results for commit 9b24bbb.

♻️ This comment has been updated with latest results.

[github-actions]

Published Unit Test Results

2 365 tests   2 365 ✅  3m 3s ⏱️
  129 suites      0 💤
    1 files        0 ❌

Results for commit 9b24bbb.

♻️ This comment has been updated with latest results.

[LiorFriedmanYahoo]

@zachaller thank you for approving. I fixed the formatting error, can you please re-run the workflows?

[LiorFriedmanYahoo]

@zachaller Can you please merge? For some reason auto merging got disabled.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[noy93845]

@zachaller hey Zach, when will this PR be merged?

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud