refactor: remove logical plan interface

[systay]

Description

In the V3 planner, the logicalPlan abstraction was useful and needed, but we haven't had this planner in the code base for some time. This PR removes this interface and all implementations of it, and changes the planner to go straight from an Operator tree to the engine Primitive tree that we use at runtime.

[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 93.10345% with 22 lines in your changes are missing coverage. Please review.

Project coverage is 68.24%. Comparing base (a1edaee) to head (7af4f5f).
Report is 4 commits behind head on main.

Files	Patch %	Lines
go/vt/vtgate/engine/sql_calc_found_rows.go	33.33%	6 Missing ⚠️
go/vt/vtgate/planbuilder/operator_transformers.go	97.46%	5 Missing ⚠️
go/vt/vtgate/planbuilder/vindex_func.go	50.00%	4 Missing ⚠️
go/vt/vttablet/tabletmanager/vdiff/table_differ.go	0.00%	3 Missing ⚠️
go/vt/vtgate/planbuilder/planner.go	84.61%	2 Missing ⚠️
go/vt/vtgate/planbuilder/route.go	90.47%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #16006   +/-   ##
=======================================
  Coverage   68.24%   68.24%           
=======================================
  Files        1562     1541   -21     
  Lines      197171   197088   -83     
=======================================
- Hits       134550   134497   -53     
+ Misses      62621    62591   -30     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[GuptaManan100]

LGTM!