[FLINK-10779][tests] Update Java / Scala StatefulJobSavepointMigrationITCase for 1.7

[hequn8128]

What is the purpose of the change

Update Java / Scala StatefulJobSavepointMigrationITCase so that it covers recovering from Flink 1.7.

Brief change log

• Support recovering from Flink 1.7 for StatefulJobSavepointMigrationITCase.

Verifying this change

This change is already covered by existing tests, such as StatefulJobSavepointMigrationITCase.java.

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): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)

[zentol]

@hequn8128 Please describe how you have generated the snapshots.

[hequn8128]

@zentol Hi, thanks a lot for the review. I guess I should generate snapshots with release-1.7.0. I will updated the pr. Thanks!

I have created another pr under FLINK-11197 to improve the comments about how to generate snapshots. Would be great if you can also take a look.

Best, Hequn

[hequn8128]

The latest PR includes snapshots generated from release-1.7.0