[FLINK-15807][docs] Add Java 11 to supported JDKs

[zentol]

Adds Java 11 to the set of supported JDKs.

Note that certain features (cassandra, hive, hbase, kafka 0.X) may not work on Java 11, but I don't know whether this is due to an incompatibility in our connector or the external server (the more likely). Hence I opted to not document this, on the assumption that users will run their stuff on a single Java version, and if they have Java 11 with a working cassandra server then the connector will likely work as well.

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[carp84]

+1, fair enough to say the Flink core could run with Java 11 smoothly now.

Meanwhile, if we're going to announce java 11 support in 1.10.0 release, hopefully somewhere we could remind our users that certain source/sink (cassandra/hbase/hive/old-version-kafka) don't support java 11 yet, to avoid possible misunderstanding. Maybe adding a release note for FLINK-10725 could do the work.

cc @GJL for notice.

[GJL]

Meanwhile, if we're going to announce java 11 support in 1.10.0 release, hopefully somewhere we could remind our users that certain source/sink (cassandra/hbase/hive/old-version-kafka) don't support java 11 yet,

I don't understand what we want to document in the release notes exactly. The description of the PR says that we do not fully understand why some connectors don't work. Can we try out all connectors on JDK11? I am against documenting things that we don't understand ourselves.

(edited)

[zentol]

We could document that we haven't tested these features on Java 11, since the backing library does not officially support Java 11.

[GJL]

I am ok with saying that we haven't tested some connectors. Is there a list of untested connectors or should we just say all of them?

[zentol]

What is listed in the PR description (Cassandra, Hive, HBase, Kafka 0.8-0.11). These are the features for which we have tests that are not being run on Java 11. We also have no e2e runs on YARN, but the IT cases are passing.

[carp84]

What is listed in the PR description (Cassandra, Hive, HBase, Kafka 0.8-0.11). These are the features for which we have tests that are not being run on Java 11. We also have no e2e runs on YARN, but the IT cases are passing.

I could see this already tracked by #10997 , so it seems the PR here is ready to go.