[wip][spark] calling merge into on DE table should not update indexed columns

[steFaiz]

Purpose

This PR is about to add a check for DataEvolutionMergeInto in Spark, to prevent users from updating global-indexed fields.
Otherwise, the indexed-scan results would be wrong.

Linked issue: none

Tests

Please see org.apache.paimon.spark.sql.RowTrackingTestBase

API and Format

None

Documentation

Will be added ASAP

[steFaiz]

Now I just simply check all indexed fields and updated fields. I think we could also push a Map<Partition, List<IndexedColumns>> or something else down to the DataEvolutionPaimonWriter, to check at the partition level.
But I don't know whether it's worth. @JingsongLi Could you please tell me your opinions?

[JingsongLi]

That's a very good question. I think we can create an option to describe what to do when data is updated. For example:

1. Index columns are not allowed to be updated.
2. Update and remove the index from the indexed column.
3. For updates without changing the index, the business is responsible for rebuilding the index.

[steFaiz]

That's a very good question. I think we can create an option to describe what to do when data is updated. For example:

@JingsongLi Thanks for your insightful advise! I've drafted this PR and will work on this! I will create an issue after conceiving a basic design and reopen this PR.