Feat: Add support for REVERSE

[pruzko]

REVERSE(x) reverses the string. Aside from SQLite, I am not aware of any engine that does not support it.

Oracle
MySQL
Postgres
TSQL

[VaggelisD]

Generally we'd want to introduce a new expression if there's a need to transpile between dialects with different semantics and/or args; For this case, it seems like we have REVERSE(x) across the board, so exp.Anonymous would be fine imo.

As a note, there are other dialects that support REVERSE like Snowflake, Spark/DB, BQ, Presto/Trino etc; If we introduced exp.Reverse without checking them first we could have broken their roundtrips, luckily they all accept a single input afaict.

With that in mind, the only use case I see for exp.Reverse would be for the type annotator.

[georgesittas]

Agreed with Vaggelis, I don't see what this PR currently achieves. Closing it for now but happy to continue discussing.

[pruzko]

I thought you're covering everything so that you can ast.find(exp.Reverse) but yeah, there is not point in adding this. Good to know tho.