Persist record merging implementation classes to table config

For CUSTOM merge mode, the list of record merging implementation classes is required for the record merging to work.  Persisting it to the table config makes it easier for query engines to know which one to use, without passing additional config.

## JIRA info

- Link: https://issues.apache.org/jira/browse/HUDI-8429
- Type: Sub-task
- Parent: https://issues.apache.org/jira/browse/HUDI-9108
- Fix version(s):
- 1.1.0

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## Comments

05/Dec/24 11:47;vinoth;Why do we need this. Can't we discover this from the merge strategy uuid;;;

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05/Dec/24 18:42;yihua;User still needs to "register" the custom merger implementation added by the user so the Hudi knows which merger classes to look up based on the merge strategy UUID.  The problem to be solved here is for the user to be able to query the table without providing an extra config of merge implementation class (which should be added in the table config), by simply adding the jar containing the merger implementation class.;;;