[FLINK-4602][State] Move RocksDB statebackend classes to o.a.f.state.rocksdb package.

[AlexYinHan]

What is the purpose of the change

This PR moves RocksDB statebackend classes to o.a.f.state.rocksdb package, so as to close FLINK-4602 and FLIP-349.

Brief change log

Move rocksdb classes from org.apache.flink.contrib.streaming.state to org.apache.flink.state.rocksdb.

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable)

[AlexYinHan]

@flinkbot run azure

[flinkbot]

CI report:

• e5da31c2709a080b083da815fd853ed262bc788a Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[AlexYinHan]

@flinkbot run azure

[AlexYinHan]

@Zakelly I have also processed the remaining 5 classes annotated with PublicEvolving, and added the license to all the new files. I also executed the command to regenerate the documentation, and the doc files remained unchanged before and after the command execution. PTAL.

ConfigurableRocksDBOptionsFactory.java
RocksDBConfigurableOptions.java
RocksDBNativeMetricOptions.java
RocksDBOptions.java
RocksDBOptionsFactory.java

[Zakelly]

@AlexYinHan Thanks for the update! I think we should keep the @PublicEvolving for those old classes.