refactor: pull out transform spec utils and definitions

[DrakeLin]

What changes are proposed in this pull request?

Moved partition value parsing, transform expression generation, and transform spec computation from log_replay.rs into a new dedicated transform_processing.rs module. This improves code organization and reusability.

This is a prefactor for CDF TransformSpec support

How was this change tested?

Existing tests

[codecov]

Codecov Report

❌ Patch coverage is 96.78899% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.39%. Comparing base (b9977cc) to head (3713575).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
kernel/src/transforms.rs	97.61%	2 Missing and 3 partials ⚠️
kernel/src/scan/log_replay.rs	75.00%	0 Missing and 1 partial ⚠️
kernel/src/table_changes/physical_to_logical.rs	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1326      +/-   ##
==========================================
+ Coverage   84.28%   84.39%   +0.11%     
==========================================
  Files         111      112       +1     
  Lines       27641    27773     +132     
  Branches    27641    27773     +132     
==========================================
+ Hits        23296    23440     +144     
+ Misses       3215     3201      -14     
- Partials     1130     1132       +2     

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[OussamaSaoudi]

just one comment. I love that we're consolidating all this.

[OussamaSaoudi]

Since there's nothing public, I think we can just make this pub(crate). If things break, just keep it pub mod

Suggested change

	pub mod transforms;
	pub(crate) mod transforms;

[OussamaSaoudi]

This isn't a breaking change, so pls remove the breaking change label.

[nicklan]

yep, l lgtm! thanks, let's just make this pub(crate) as Oussama suggested

[DrakeLin]

This isn't a breaking change, so pls remove the breaking change label.

booo github actions booooo