allow multiple ldap bootstrap files for integration tests

[jihoonson]

Description

This PR allows the LDAP integration tests to read multiple bootstrap files so that you can add more configuration files for testing your custom extensions. It also changes the host port bound for metadata store as it can conflict when you have mysql running.

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This PR has:

• been self-reviewed.
  • using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• added documentation for new or modified features or behaviors.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[jon-wei]

LGTM after CI