[FLINK-39322][table] Add restore tests for cascaded delta join

[Au-Miner]

What is the purpose of the change

Add restore tests for cascaded (3-table) delta join scenarios to ensure state compatibility across versions when upgrading from stream-exec-delta-join version 1 to version 2.

Brief change log

• Add 7 new cascaded delta join test programs in DeltaJoinTestPrograms covering join-key-equals-index, join-key-contains-index, non-equiv-condition, calc-on-source, filter-pushed-down, cache, and cache-with-calc-on-source.
• Register the new programs in DeltaJoinRestoreTest#programs() and override programsToIgnore() to skip cascaded programs for version 1 (only supported from version 2).
• Add corresponding JSON plan files and savepoint _metadata under restore-tests/stream-exec-delta-join_2/.

Verifying this change

This change itself adds restore tests. The new test programs are exercised by DeltaJoinRestoreTest which validates that a job restored from a version-2 savepoint produces the expected materialized output for each cascaded delta join variant.

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, 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

[flinkbot]

CI report:

• 215b4c4 Azure: SUCCESS

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