Added support for SQLite triggers

[LucaCappelletti94]

This PR:

• EnablesCREATE TRIGGER for SQLite dialect, which was early blocked by a dialect guard
• Adds support for TEMPORARY triggers - at this time, I have not added a dialect guard on the use of the TEMPORARY keyword, which may be desirable if we want to raise errors in other dialect if TEMP triggers are provided.
• Adds support for optional FOR EACH ROW in triggers, which is optional in SQLite
• Adds test suite for several CREATE TRIGGER cases in SQLite.
• Enables DROP TRIGGER for SQLite dialect, which was early blocked by a dialect guard
• Adds test suite for a DROP TRIGGER case in SQLite.

Closes issue #2023

[iffyio]

Suggested change

	if !dialect_of!(self is SQLiteDialect ) {
	self.expect_keyword_is(Keyword::FOR)?;
	}
	self.expect_keyword_is(Keyword::FOR)?;

Can we skip the dialect guard here?

[iffyio]

Seems this comment is unresolved? ideally we want to skip dialect_of checks where possible

[LucaCappelletti94]

Regarding commit c893bda, it should be noted that the MsSQL parser for triggers is incorrect, as it does not include much of their syntax, and currently always adds in a FOR STATEMENT, which is incorrect. This is clearly way outside the current PR objectives though. I have patched the parse trigger so that it would be compatible with the MsSQL tests, but I am completely unfamiliar with that dialect so I would leave a more refined extension to somebody more familiar with it.