This commit implements parsing support for all previously TODO-marked test
cases from the ClickHouse test suite. Key additions include:

Parser enhancements:
- WITH scalar expressions (WITH 1 AS x SELECT x)
- LEFT ARRAY JOIN clause
- Tuple element access via dot notation (t.1)
- CREATE MATERIALIZED VIEW with ENGINE clause
- CREATE TABLE with flexible clause ordering (PARTITION BY, ORDER BY, etc.)
- SYSTEM commands with keywords (TTL MERGES, SYNC REPLICA, etc.)
- SHOW/DESCRIBE commands with dotted table names (system.one)
- USE statement with keyword database names (USE default)
- Keywords usable as function names (format(), etc.)

Token additions:
- NULL_SAFE_EQ (<=>) operator

AST additions:
- TupleAccess for named tuple element access
- Extended CreateQuery with To and Populate fields
- Extended ShowQuery with Database field

All 93 previously skipped test cases now pass.