fix: Parse LTRIM/RTRIM functions as positional exp.Trim

[VaggelisD]

Fixes #3957

Docs

Oracle RTRIM | Clickhouse TRIM

[cpcloud]

This PR seems to have broken LTRIM and RTRIM that strip multiple characters in Oracle.

TRIM doesn't allow multiple characters, but LTRIM and RTRIM do.

Unfortunately the docs don't state this requirement explicitly anywhere: https://docs.oracle.com/en/database/oracle/oracle-database/23/sqlrf/TRIM.html#GUID-00D5C77C-19B1-4894-828F-066746235B03

If you try to run any TRIM call with more than one trim character then you'll get this error message:

E   oracledb.exceptions.DatabaseError: ORA-30001: trim set should have only one character
E   Help: https://docs.oracle.com/error-help/db/ora-30001/

[VaggelisD]

That checks out:

SELECT TRIM(LEADING 'ab' FROM 'abc')
       *
ERROR at line 1:
ORA-30001: trim set should have only one character

vs

SELECT LTRIM('abc', 'ab');
'c'

Also relevant SO thread.

So for Oracle, we can probably do the following:

• If we have LEADING or TRAILING positional specifiers and multiple remove characters, we should force LTRIM and RTRIM generation respectively
• For other cases (e.g. BOTH specifier, 0 or 1 remove chars) we can keep the existing representation: TRIM(<position> <remove char> FROM <string>

[georgesittas]

Let's just keep it simple and always do LTRIM and RTRIM for LEADING and TRAILING, respectively. No need to make it complicated.