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

[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.

[LucaCappelletti94]

Is there anything else needed to be done for this PR? @iffyio

[iffyio]

@LucaCappelletti94 could you take a look at this comment?

[LucaCappelletti94]

Hi @iffyio, I replied to it here: #2037 (comment)

[iffyio]

@LucaCappelletti94 the link takes me to the top of the page not sure why but I'm unable to find the comment in this case

[LucaCappelletti94]

@LucaCappelletti94 the link takes me to the top of the page not sure why but I'm unable to find the comment in this case

@iffyio Here follows the comment:

So, if you mean to refactor this into:

} else {
    None
};

would simply make it more permissive and allow for parsing stuff that does not make sense in some dialects.

Conversely, the following:

} else {
    self.expect_keyword_is(Keyword::FOR)?;

    None
};

would crash for valid SQLite statements.

[iffyio]

LGTM! Thanks @LucaCappelletti94!