[DBMON-5685] Ensure innodb lock queries respect disable_innodb_metrics config option

[eric-weaver]

What does this PR do?

Originally we checked for disable_innodb_metrics before our innodb query to SHOW INNODB STATUS but we've since extended support for querying for deadlocks from information_schema.INNODB_METRICS. This second query isn't currently excluded when disabling innodb metrics which leads to a consistent query exception when using a different mysql engine or very old Mysql versions that don't have information_schema.INNODB_METRICS table.

We already check if InnoDB engine is in use before issuing these queries, but if INNODB_METRICS table doesn't exist it will crash. This change moves evaluation of the disable_innodb_metrics config value into our _check_innodb_engine_enabled function so that it's respected everywhere we query innodb allowing customers to disable them if desired.

Motivation

This issue was raised in https://datadoghq.atlassian.net/browse/SDBM-2053

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[codecov]

Codecov Report

❌ Patch coverage is 16.66667% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.10%. Comparing base (6ba0f52) to head (79a2295).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

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