feat: support subqueries for shard selection

[levkk]

Refactor the query parser to be completely recursive. Use the same parser for SELECT and DELETE queries. This adds support for extracting the sharding key filter from pretty much anywhere in the query, as long as it follows our supported format:

key = $1 OR key IN ($1, $2, $3) OR key = ANY($1)

fix #653

TODOs:

1. Use new parser for UPDATE and INSERT statements. Requires integration with Query rewrite engine 3.0 (part 1 of many) #637 (split rewrite engine from parser).

[codecov]

Codecov Report

❌ Patch coverage is 91.92340% with 97 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog/src/frontend/router/parser/statement.rs	91.83%	89 Missing ⚠️
pgdog/src/frontend/router/parser/column.rs	84.00%	4 Missing ⚠️
pgdog/src/frontend/router/parser/table.rs	40.00%	3 Missing ⚠️
pgdog/src/backend/replication/sharded_tables.rs	95.45%	1 Missing ⚠️

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[blacksmith-sh]

Found 3 test failures on Blacksmith runners:

Failures

Test	View Logs
unbans all pools	View Logs
connection/tcp broken database both down unbans all pools	View Logs
crud_spec/CRUD and Join for Customer and Order does full CRUD and join	View Logs