refactor: cleaner cloning API

[systay]

Refactor: Simplify Clone Usage with Generics

Summary

This PR refactors the codebase to use a more generic Clone method, eliminating the need to specify exact types when cloning various structures. This makes the code cleaner and more maintainable.

Changes

• Updated various usages of specific clone methods (e.g., CloneSimpleTableExpr, CloneSQLNode, CloneRefOfParsedComments, CloneRefOfColumnDefinition, etc.) to use the generic sqlparser.Clone.

Rationale

Using a generic Clone method reduces redundancy and potential for errors. It also enhances the maintainability of the code by centralizing cloning logic.

Impact

This refactor should have no functional impact on existing features but will make the code easier to work with.

[vitess-bot]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

• Ensure that the Pull Request has a descriptive title.
• Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

Tests

• Bug fixes should have at least one unit or end-to-end test, enhancement and new features should have a sufficient number of tests.

Documentation

• Apply the release notes (needs details) label if users need to know about this change.
• New features should be documented.
• There should be some code comments as to why things are implemented the way they are.
• There should be a comment at the top of each new or modified test to explain what the test does.

New flags

• Is this flag really necessary?
• Flag names must be clear and intuitive, use dashes (-), and have a clear help text.

If a workflow is added or modified:

• Each item in Jobs should be named in order to mark it as required.
• If the workflow needs to be marked as required, the maintainer team must be notified.

Backward compatibility

• Protobuf changes should be wire-compatible.
• Changes to _vt tables and RPCs need to be backward compatible.
• RPC changes should be compatible with vitess-operator
• If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

Attention: Patch coverage is 88.40580% with 8 lines in your changes missing coverage. Please review.

Project coverage is 68.22%. Comparing base (87ecae7) to head (9d78ad3).

Files	Patch %	Lines
go/vt/vtgate/simplifier/simplifier.go	71.42%	4 Missing ⚠️
go/vt/vttablet/onlineddl/executor.go	33.33%	2 Missing ⚠️
go/vt/vtgate/planbuilder/operators/table.go	0.00%	1 Missing ⚠️
go/vt/vtgate/vschema_manager.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16079      +/-   ##
==========================================
+ Coverage   68.19%   68.22%   +0.02%     
==========================================
  Files        1541     1541              
  Lines      197369   197371       +2     
==========================================
+ Hits       134605   134650      +45     
+ Misses      62764    62721      -43     

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[vitess-bot]

Hello! 👋

This Pull Request is now handled by arewefastyet. The current HEAD and future commits will be benchmarked.

You can find the performance comparison on the arewefastyet website.