Support for Postgres END semantics

[tobyhede]

I've run into an interesting conundrum.

In PostgreSQL, END is a synonym for COMMIT.
END is currently not supported. Parsing an END statement returns nothing.

One wrinkle is that Keyword::END is used as a statement delimiter in parse_statements.

Token::Word(word) if word.keyword == Keyword::END => break,

https://github.com/sqlparser-rs/sqlparser-rs/blob/main/src/parser/mod.rs#L423

I am attempting to add support for the Postgres END/COMMIT semantics.
The logic is quite simple, but END is never parsed because the break is hit first.

A bit lost as to how to approach changing this logic.