sql: statement hints do not apply inside routines

Statements within routines do not currently respect hint injections. Here's an example:

```sql
CREATE TABLE olympians (
name STRING,
sport STRING,
INDEX (name) STORING (sport)
);

EXPLAIN SELECT sport FROM olympians WHERE name = 'Apolo Ohno';
-- constrained scan of olympians_name_idx

SELECT information_schema.crdb_rewrite_inline_hints(
'SELECT sport FROM olympians WHERE name = _',
'SELECT sport FROM olympians@olympians_pkey WHERE name = _'
);

EXPLAIN ANALYZE SELECT sport FROM olympians WHERE name = 'Apolo Ohno';
-- full scan of olympians_pkey

CREATE FUNCTION ohno() RETURNS STRING LANGUAGE SQL STABLE AS $$
SELECT sport FROM olympians WHERE name = 'Apolo Ohno';
$$;

SELECT ohno();
-- does not use olympians_pkey
```

Jira issue: CRDB-59564

Epic CRDB-66209