[Refactor] Add subquery support for formatter

[colinthebomb1]

Overview:

This PR implements subquery support for the formatter, as well as simplifies the process for comparing input sql to output sql by using mosqlparse instead of string comparison with regex

Code Changes:

• In tests\test_formatter.py added test_subquery_format() to run a formatter test that uses a sql query containing a subquery
• Removed normalize_sql function and changed input/output sql comparisons to use mosqlparse

[Copilot]

Pull request overview

Adds formatter support for SQL subqueries and makes formatter tests compare SQL semantics by parsing (mo_sql_parsing) rather than normalizing strings.

Changes:

• Update formatter expression serialization to handle subqueries and string literals in mo_sql_parsing-compatible JSON.
• Refactor formatter tests to compare mo_sql_parsing.parse() output instead of regex/whitespace normalization.
• Add/enable a formatter test case that includes a subquery.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tests/test_query_formatter.py	Switches SQL comparisons to parse() and adds a subquery formatting test.
core/query_formatter.py	Extends expression formatting to emit mo_sql_parsing JSON for string literals and subqueries.

Comments suppressed due to low confidence (1)

tests/test_query_formatter.py:84

• The PR description mentions updating tests/test_formatter.py, but the changes/additions are actually in tests/test_query_formatter.py. Please update the PR description (or rename/move the test) so the documented change matches the code.

def test_subquery_format():
    # Tables
    emp_table = TableNode("employee")

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