[FLINK-40518][checkpointing] Only enable checkpointing-during-recovery when unaligned checkpoints are enabled

[1996fanrui]

What is the purpose of the change

CheckpointingOptions.isCheckpointingDuringRecoveryEnabled gated only on
UNALIGNED_RECOVER_OUTPUT_ON_DOWNSTREAM and CHECKPOINTING_DURING_RECOVERY_ENABLED, not on whether
unaligned checkpoints are enabled. But checkpointing during recovery only works on the unaligned
(alternating()) barrier-handler path; with unaligned checkpoints disabled the aligned path gets a NO_OP
recovery trigger, so a checkpoint triggered mid-recovery can neither be taken nor declined and hangs until
it expires, leading to a failover loop. This adds the missing precondition so such jobs fall back to the
tested non-CDR recovery path.

Brief change log

• [FLINK-40518] Also require unaligned checkpoints to be enabled in CheckpointingOptions#isCheckpointingDuringRecoveryEnabled (the single central gate for all CDR call sites).

Verifying this change

This change added a unit test:

• Extended CheckpointingOptionsTest to assert CDR requires unaligned checkpoints enabled (and is disabled otherwise).

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: yes (checkpointing during recovery)
• 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

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CI report:

• acf1068 Azure: SUCCESS

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