Fix SET and START TRANSACTION in create procedure statements

[GuptaManan100]

Description

As stated in #18278, when we added support for create procedures in #17946, we made a couple of mistakes -

1. SET y = 4 statements get converted to SET @@y = 4 which is incorrect. This was happening in the normalisation step of the planner. This has been fixed in this PR by skipping the entire normalisation step for create procedure statements.
2. START TRANSACTION statements get converted to BEGIN which eventually throw a parsing error. In a stored procedure a BEGIN statement is considered part of a BEGIN...END statement, so we need to preserve START TRANSACTION statements as is, and not change them to BEGIN. This is done by storing a new field in the AST to preserve the original type of the statement.

Tests for both of these have been added to the planner as well as e2e tested that we are indeed able to create the procedures with these statements.

Related Issue(s)

• Fixes Bug Report: SET and START TRANSACTION statements in CREATE PROCEDURE don't work as intended #18278

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

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[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 67.46%. Comparing base (c3daef3) to head (8bfc73d).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/sqlparser/ast_format.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18279      +/-   ##
==========================================
- Coverage   67.46%   67.46%   -0.01%     
==========================================
  Files        1602     1602              
  Lines      262245   262245              
==========================================
- Hits       176930   176926       -4     
- Misses      85315    85319       +4     

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