[Bug] Flink action factories do not report which required argument is missing

[thswlsqls]

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• I searched in the issues and found nothing similar.

Paimon version
master @ b15bda5 (2.1-SNAPSHOT)

Compute Engine
Flink

Minimal reproduce step
Run an action jar and omit one required argument:

flink run paimon-flink-action-*.jar create_tag_from_timestamp \
  --warehouse <wh> --database d --table t --tag tg      # --timestamp omitted

Four required arguments are read with params.get(...) and dereferenced immediately, instead of params.getRequired(...) used by every sibling argument in the same methods:

• MergeIntoActionFactory.create() line 83 — merge_actions
• CreateTagFromTimestampActionFactory.create() line 41 — timestamp
• CreateTagFromWatermarkActionFactory.create() lines 42, 43 — tag, watermark

What doesn't meet your expectations?
Expected: Argument 'timestamp' is required. Run '<action> --help' for more information., as produced by MultipleParameterToolAdapter.getRequired() and by DropPartitionActionFactory/MarkPartitionDoneActionFactory.
Actual: a bare java.lang.NumberFormatException: null (timestamp, watermark) or java.lang.NullPointerException (merge_actions), neither of which names the missing argument.

Anything else?
Same class of defect as #8611, which fixed only the migrate_* factories.

Are you willing to submit a PR?

• I'm willing to submit a PR!