[FLINK-28520][runtime] RestClient doesn't use SNI TLS extension

[jd-hatzenbuhler]

What is the purpose of the change

This pull request makes the RestClient us of the TLS SNI extension

Brief change log

The RestClient create the socket when the target Host and Port is known instead of during instanciation.

Verifying this change

This change added tests and can be verified as follows:

• Added integration tests to test TLS SNI extension

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): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): don't know
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: don't know
• 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

[flinkbot]

CI report:

• f32e97c6df70965c37d40ca3eed74f9b4cd2f16a Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

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

[jd-hatzenbuhler]

https://github.com/apache/flink/commit/ff64ef0e5f286ba62338832cd68aff60196b1f42 Azure: SUCCESS https://github.com/apache/flink/commit/762072e91fa661807f6ab08ea9030216e80b6aa8 Azure: SUCCESS https://github.com/apache/flink/commit/d645f416a21305bd67b7d9b1fc66288987aa258e Azure: SUCCESS https://github.com/apache/flink/commit/009a1b909ee8351ffc54ea5b1ede54f9570dac59 Azure: SUCCESS

[jd-hatzenbuhler]

Not needed anymore for our use case