Add pseudo tables

[Huliiiiii]

Close #842

[Expurple]

To we really need these special variants? These table names look like they can be already expressed as "regular" table names: ColumnRef::from(("OLD", MyColumn))

It may be enough to define some unit-struct idens for these tables and document the approach.

[Huliiiiii]

prepare_iden will quote them, but they cannot be quoted.

[Expurple]

Ok, I see. Then, I wouldn't change ColumnRef at all. We don't need to do anything with the "column basename" part. We need to somehow allow unquoted TableNames (which would then be stored in ColumnRef as usual) and provide a way to construct unquoted TableNames ergonomically

[Expurple]

Also, your current approach doesn't support asterisk, like NEW.* (literally * in the query)

[Huliiiiii]

Also, your current approach doesn't support asterisk, like NEW.* (literally * in the query)

This means the glob pattern, not the SQL asterisk.

[Expurple]

I understand. I'm pointing out that the SQL asterisk is also valid with these tables. I'd like to find a clean way to support it right away

[Huliiiiii]

I think we could add an enum of pseudo tables/columns and regular idens.
Basically it’s just raw idens vs regular ones.
One hacky approach is to check in prepare_iden if the iden is one of the specific keywords.