Handle the sql type named LONG

### Motivation

People using the native engine may write `CAST( some AS LONG )` because they used to work with those types - however the sql parser doesn't know that type and returns an error.

### Description

It could be handled as an alias to `BIGINT`

Start by locating the SQL parser's type handling for CAST and the existing handling or tests for BIGINT. Add coverage showing that LONG is accepted as an alias for BIGINT, then run the relevant SQL parser tests to confirm CAST expressions no longer fail.

Written by the indexing model from the issue text.