[dbm] Add migrations tracking

[dalextorres]

What does this PR do?

Motivation

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

[datadog-official]

⚠️ Tests

✨ Fix all issues with Cursor

⚠️ Warnings

🧪 1 Test failed

test_all_config_defaults from test_config_defaults.py (Datadog) (Fix with Cursor)

================================================================================
MISSING EXPECTED DEFAULTS!
================================================================================

The following fields exist in InstanceConfig but are missing from EXPECTED_DEFAULTS:
  ['collect_migrations']

To fix this:
...

ℹ️ Info

❄️ No new flaky tests detected

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