Refactor merge to support partial update

[chenjian2664]

Description

Currently the update implementation of MERGE update updates the whole row, this pr is going to update the engine merge impl to support partial update.
The main idea is to keep the merge case_number of the UpdateCase in the output of the MergeProcessNode,(this value already kept in the merge_row symbol that in the sourceNode of the MergeProcessNode, so only needs to project it), and then in the MergeWriterNode, the updateSink can perform the update according to the update case.

The partial update also needs to know the mapping of the case number with the relevant columns, thus the ConnectorMetadata#beginMerge is refactored to hold the info.

Here use the Phoenix connector as a example to show how it works.

Additional context and related issues

Prerequisites for #23034

Release notes

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## Section
* Support partial update in engine.
* Support partial update in Phoenix.

[djsagain]

This looked pretty good to me. Thanks for undertaking this work!

The PR needs Phoenix tests that show that only updated columns are changed. The tests need to cover cases where a single column is updated in a single row and in multiple rows; where non-overlapping sets of columns are updated in different cases; and tests that include UPDATE as well as INSERT and DELETE cases.

We also need @electrum to take a look.

[chenjian2664]

Flaky https://github.com/trinodb/trino/actions/runs/11821799275/job/32937454502?pr=24075#step:5:2219

[chenjian2664]

https://github.com/trinodb/trino/actions/runs/11829608194/job/32961756024?pr=24075#step:5:2343

[chenjian2664]

https://github.com/trinodb/trino/actions/runs/11829608194/job/32961756024?pr=24075#step:5:2343

#24131

[djsagain]

I'm approving this PR, but we still need @electrum to take a look. I'll ping him now about it.

[kokosing]

Reviewed initially first commit.

[electrum]

Thanks!