Laura.hampton/envoy additional metrics

[lgh2]

In progress, please don't merge

What does this PR do?

Adds additional metrics to the Envoy integration

Motivation

Customer request

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

[FlorentClarret]

Hi @lgh2 👋 FYI code freeze is coming this Friday and we will release the integrations right after. Let us know if you want this to be shipped with 7.40 and if you need help with @yzhan289's comments

[FlorentClarret]

As discussed with @lgh2, I'm taking care of this one 🙂

[codecov[bot]]

Codecov Report

Merging #12668 (32f5390) into master (79dbdd1) will decrease coverage by 0.14%. The diff coverage is n/a.

Flag	Coverage Δ
datadog_checks_dev	79.96% <ø> (-2.51%)	:arrow_down:

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

[FlorentClarret]

See https://github.com/DataDog/integrations-core/pull/14088 and its description.