Add missing etcd metrics

[arapulido]

What does this PR do?

There have been several metrics added upstream that were not reflected in the integration. This PR adds those.

Motivation

I am working on creating a new OOTB dashboard for etcd, but for it, I need the new metrics to be available.

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

[github-actions[bot]]

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

[codecov[bot]]

Codecov Report

Merging #12715 (bdb0baf) into master (8b4acc6) will increase coverage by 0.00%. The diff coverage is 100.00%.

Flag	Coverage Δ
etcd	93.96% <100.00%> (+0.08%)	:arrow_up:

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