fix: schema evolution for merge operation

[JustinRush80]

Description

Fix Schema Evolution in MERGE operation when there are chained expression such as
when_not_matched_insert_all().when_matched_update_all().execute()

Related Issue(s)

• closes [Bug]: Table merging fails with merge_schema=True #3943

Documentation

[github-actions]

ACTION NEEDED

delta-rs follows the Conventional Commits specification for release automation.

The PR title and description are used as the merge commit message. Please update your PR title and description to match the specification.

[codecov]

Codecov Report

❌ Patch coverage is 95.65217% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.21%. Comparing base (948396f) to head (e6d049c).

Files with missing lines	Patch %	Lines
crates/core/src/operations/merge/mod.rs	95.65%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3945       +/-   ##
===========================================
+ Coverage   26.24%   74.21%   +47.96%     
===========================================
  Files         124      152       +28     
  Lines       19824    39614    +19790     
  Branches    19824    39614    +19790     
===========================================
+ Hits         5203    29399    +24196     
+ Misses      14251     8885     -5366     
- Partials      370     1330      +960     

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