Implement StartTLS protocol for Mysql

[dpavlov-smartling]

What does this PR do?

This PR adds support for StartTLS implementation of Mysql protocol

Motivation

Similar to PR #12596 we need to monitor SSL/TLS certificate expiration dates on remote Mysql servers

Additional Notes

Had to increase sleep from 5 to 20 seconds in tls/tests/conftest.py to give Mysql docker container time to initialize default database. More details on https://hub.docker.com/_/mysql in section "No connections until MySQL init completes"

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
• If the PR doesn't need to be tested during QA, please add a qa/skip-qa label.

[github-actions]

Test Results

    4 files      4 suites   1m 24s ⏱️
  54 tests   53 ✔️ 1 💤 0 ❌
110 runs  106 ✔️ 4 💤 0 ❌

Results for commit f5f1cd4.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

Merging #14352 (f5f1cd4) into master (7908836) will increase coverage by 0.01%.
The diff coverage is 96.87%.

Flag	Coverage Δ
tls	92.07% <96.87%> (+1.10%)	⬆️

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

[dpavlov-smartling]

• Not sure how to fix "Validate repository" - "validate third-party license metadata". Attempt to run ddev validate licenses on local environment throws "ReadError: not a gzip file"
• Check "PR / test / submit-traces / Submit traces (pull_request)" failed because it wasn't able to start container for the verification: Failed to initialize container gcr.io/datadoghq/agent:latest

[ofek]

Looks good to me, thanks!