[FLINK-12840] fix network utils to work with ipv6 correctly

[ppotseluev]

What is the purpose of the change

It fixes problems when using flink with ipv6.

Brief change log

• Fixed AkkaUtils.getRemoteAkkaConfig to work with ipv6 addresses in typesafe config.
• Fixed NetUtils.unresolvedHostToNormalizedString to work with already normalized ipv6 addresses.

Verifying this change

Added test cases to AkkaUtilsTest and NetUtilsTest.

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

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

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

[flinkbot]

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Review Progress

• ✅ 1. The [description] looks good.
  • Approved by @StephanEwen [PMC]
• ✅ 2. There is [consensus] that the contribution should go into to Flink.
  • Approved by @StephanEwen [PMC]
• ❓ 3. Needs [attention] from.
• ✅ 4. The change fits into the overall [architecture].
  • Approved by @StephanEwen [PMC]
• ✅ 5. Overall code [quality] is good.
  • Approved by @StephanEwen [PMC]

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[rmetzger]

Thanks a lot for this contribution. Flink has a very ambitious roadmap for the upcoming 1.9 release, that's why many committers are quite busy finishing up their work.
You might experience a little delay in the review of this change, but we'll still try to give you feedback as soon as possible.
Thanks again!

[StephanEwen]

@flinkbot approve all

[StephanEwen]

Thanks for reporting this. The fix looks good and correct, the tests make sense.

Will merge this...