Add deprecation check for Java version

[gwbrown]

Adds a deprecation check for Java version, as Java 11 will be required
in the next version of Elasticsearch.

Relates to #40756 and #40754

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Marked as a draft because this will cause test failures when running on jdk8, as there exist tests which assume there are no deprecation warnings under normal testing circumstances.

[elasticmachine]

Pinging @elastic/es-core-features

[gwbrown]

This has been sitting idle for a while, and given 1) the difficulties testing this, and especially 2) the fact that our default download bundles a JDK now, this is unlikely to be an issue that most customers will run into. We can revisit this leading up to the release of the next major version if necessary.

[jasontedor]

@gwbrown I think that we can add an exclusion to the test framework for this specific deprecation (as we've done, for example with the migration to one shard in the past). I do think that we should have this deprecation check, as a major JDK version upgrade can be a hurdle for some users, we should notify them of that change as soon as possible.

[gwbrown]

@jasontedor Thanks for the input - you're more familiar with what users have difficulties with, so I'll reopen and work on updating this PR.

[gwbrown]

Closing in favor of #64996