Add config spec and models

[fanny-jiang]

What does this PR do?

Updates the prometheus check with config spec and models. It also uses the instance/default config template so that it will stay up to date with any new config options added to the base check.

Motivation

Community

Additional Notes

Review checklist (to be filled by reviewers)

• [ ] Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• [ ] PR title must be written as a CHANGELOG entry (see why)
• [ ] Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• [ ] PR must have changelog/ and integration/ labels attached

[codecov[bot]]

Codecov Report

Merging #12714 (5d53033) into master (776d6fd) will not change coverage. The diff coverage is n/a.

Flag	Coverage Δ
prometheus	94.17% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

[github-actions[bot]]

The validations job has failed; please review the Files changed tab for possible suggestions to resolve.

[github-actions[bot]]

The validations job has failed; please review the Files changed tab for possible suggestions to resolve.

[github-actions[bot]]

The validations job has failed; please review the Files changed tab for possible suggestions to resolve.