Bound nested SELECT parsing to MAX_PARSER_DEPTH

[nilox94]

Issue

MAX_PARSER_DEPTH is only checked in parse_expression_rec. Nested SELECT in FROM (...), CTEs, IN (SELECT ...), and scalar subqueries call parse_select_statement without enter_depth(). Subquery nesting has no limit. On deep input the parser stack-overflows instead of returning a parse error.

Repro

On main, with a fresh build (cargo build --bin clickhouse-analyzer):

SELECT 1 FROM (SELECT 1 FROM (SELECT 1 FROM (...)))  -- repeated 10,000 times

python3 -c "s='SELECT 1'; [s:=f'SELECT 1 FROM ({s})' for _ in range(10_000)]; print(s)" \
  | cargo run --bin clickhouse-analyzer
# thread 'main' has overflowed its stack
# fatal runtime error: stack overflow

Fix

Add parse_nested_select_statement(). It wraps enter_depth() and leave_depth() around parse_select_statement(). Use it at subquery entry points:

• parse_subquery_table_ref (FROM (SELECT …))
• parse_with_items (CTEs)
• parse_in_rhs / expr_delimited (IN (SELECT …), (SELECT …))

Top-level SELECT and UNION RHS are unchanged. They are not nested inside another depth-consuming frame.

Adds bounds_deeply_nested_subqueries: 1001 nested SELECT * FROM (...) wrappers return a nesting-depth error; 999 parse cleanly.

Verify

After this PR, the same query at depth 1001 returns "Maximum expression nesting depth exceeded" without crashing.

cargo test bounds_deeply_nested_subqueries