sql: consider retaining comments in routine body

Currently, we discard all SQL comments from the routine body:
```sql
CREATE PROCEDURE p(OUT INT) LANGUAGE SQL AS $$
-- inline comment
SELECT 1;
$$;

SELECT create_statement FROM [SHOW CREATE PROCEDURE p];
```
```
CREATE PROCEDURE public.p(OUT INT8)
LANGUAGE SQL
SECURITY INVOKER
AS $$
SELECT 1;
$$
```
We should consider retaining the comments in some way (e.g. storing the original SQL string in a separate field somewhere), ideally inlined in the body.

There is some discussion [here](https://cockroachlabs.slack.com/archives/G01R3EYPQKA/p1732563045609389).

Jira issue: CRDB-44900