Revisit payload and merge config handling

[hudi-bot]

A few TODOs:

[https://github.com/apache/hudi/pull/13615/#discussion_r2274253729]

[https://github.com/apache/hudi/pull/13615/#discussion_r2274271097]

[https://github.com/apache/hudi/pull/13615/#discussion_r2274346707]

[https://github.com/apache/hudi/pull/13615/#discussion_r2277390249]

[https://github.com/apache/hudi/pull/13615/#discussion_r2277504954]

[https://github.com/apache/hudi/pull/13615/#discussion_r2277511364]

[https://github.com/apache/hudi/pull/13615/#discussion_r2277516019]

[https://github.com/apache/hudi/pull/13615/#discussion_r2277524874]

[https://github.com/apache/hudi/pull/13615/#discussion_r2277532615]

[https://github.com/apache/hudi/pull/13615/#discussion_r2277550470]

[https://github.com/apache/hudi/pull/13615/#discussion_r2277556629]

[https://github.com/apache/hudi/pull/13615/#discussion_r2277599931]

https://github.com/apache/hudi/pull/13615/#discussion_r2277685486

JIRA info

• Link: https://issues.apache.org/jira/browse/HUDI-9718
• Type: Improvement
• Fix version(s):
  • 1.1.0