minor: Upgrade to Hadoop 3.5

[jtuglu1]

Description

https://hadoop.apache.org/release/3.5.0.html

Release note

Upgrade to Hadoop 3.5 and push minimum supported JDK to 21

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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.
• a release note entry in the PR description.
• 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.

[gianm]

Is this PR dropping support for Java 17? Why? I don't have anything against it in principle, but there should be a reason.

[jtuglu1]

I believe this was the plan all-along (wait for Hadoop 3.5 upgrade then bump to whatever latest JDK version this supports). Since Hadoop 3.5 supports JDK 21 client-side and it is the only thing preventing us from upgrading the compiler version, it seemed correct to do. Whether we wait for JDK 25+ support in Hadoop before decoupling it from critical extensions (e.g. Parquet) is IMO a separate issue, and we can in the meantime upgrade the compiler version as the timeline for the other changes is undefined at the moment. Let me know if you have any hesitations.