Handle metadata collection flag on MetadataManager

[florimondmanca]

What does this PR do?

Deprecate AgentCheck.is_metadata_collection_enabled() in favor of filtering submissions directly on MetadataManager.

TODO: actually this doesn't prevent integrations from doing unnecessary processing to retrieve metadata (eg fetching the version), which is probably why we added is_metadata_collection_enabled() in the first place. Hmm…

Motivation

• Remove the need to always check for is_metadata_collection_enabled() in integrations, reducing boilerplate and potential for errors.
• Immediately add support for honoring enable_metadata_collection Agent flag to all integrations. (Otherwise we're going to have and add an if statement to all our integrations, eg see Allow disabling metadata collection in fluentd #6061.)

Additional Notes

• is_metadata_collection_enabled originally added in Add a utility method to check if metadata collection is enabled #5748.

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]

Codecov Report

Merging #6077 into master will increase coverage by 0.95%.
The diff coverage is 100%.

Impacted Files	Coverage Δ
datadog_checks_base/tests/test_agent_check.py	99.46% <ø> (-0.02%)	⬇️
datadog_checks_base/tests/test_metadata.py	92.38% <100%> (+0.19%)	⬆️
...ks_base/datadog_checks/base/utils/metadata/core.py	100% <100%> (ø)	⬆️
...atadog_checks_dev/datadog_checks/dev/structures.py	81.96% <0%> (-4.92%)	⬇️
...dog_checks_base/datadog_checks/base/checks/base.py	84.28% <0%> (-0.29%)	⬇️
lighttpd/datadog_checks/lighttpd/__init__.py
supervisord/datadog_checks/supervisord/__init__.py
gearmand/datadog_checks/gearmand/gearmand.py
twistlock/datadog_checks/twistlock/twistlock.py
mapreduce/tests/test_mapreduce_integration_e2e.py
... and 364 more

[florimondmanca]

Closed, as integrations typically need to make processing to retrieve the version, and we'd want to prevent that processing from happening too, which this doesn't solve.