[FLINK-26354] -restoreMode should be --restoreMode and should have a shorthand

[dawidwys]

What is the purpose of the change

Add shorthand option for restoreMode

Verifying this change

     -rm,--restoreMode <arg>                    Defines how should we restore
                                                from the given savepoint.
                                                Supported options: [claim -
                                                claim ownership of the savepoint
                                                and delete once it is subsumed,
                                                no_claim (default) - do not
                                                claim ownership, the first
                                                checkpoint will not reuse any
                                                files from the restored one,
                                                legacy - the old behaviour, do
                                                not assume ownership of the
                                                savepoint files, but can reuse
                                                some shared files.

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, Kubernetes/Yarn, 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)

[dawidwys]

cc @Myasuka @rkhachatryan @pnowojski

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Last check on commit f4c9997 (Fri Feb 25 08:29:11 UTC 2022)

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[Myasuka]

Thanks for creating this PR. I have left some comments, please take a look.

[Myasuka]

Thanks for the update, LGTM

[knaufk]

LGTM