[BUG] `ALTER TABLE ... MODIFY/DROP` should support the `IF EXIST` option

[manticore-projects]

Discussed in #2111

^{Originally posted by dani-petrov November 19, 2024}
Hello, I will attach a screenshot of the currently supported syntax for Alter Table -> modify column:

Looking at the circled part, the correct syntax for a MODIFY [COOUMN] statement is together with [IF EXISTS] and not [IF NOT EXISTS]. This leads to failed parsing. Is it possible to allow both IF NOT EXISTS and IF EXISTS?
Thank you!