Support exiting scope before last field #[scope(exit_before)]

[overlookmotel]

oxc_ast_tools recognises #[scope(enter_before)] to mark a field as the start of the scope in a type. We also need #[scope(exit_before)] for #6270.

Note: I think #[scope(exit_before)] is better than #[scope(exit_after)] because attributes go before fields, so it reads more clearly:

pub struct TSConditionalType<'a> {
    pub span: Span,
    pub check_type: TSType<'a>,
    #[scope(enter_before)]
    pub extends_type: TSType<'a>,
    pub true_type: TSType<'a>,
    #[scope(exit_before)]
    pub false_type: TSType<'a>,
    pub scope_id: Cell<Option<ScopeId>>,
}

We will need to build support for this into both:

1. oxc_ast_tools and the Visit / VisitMut generator.
2. oxc_traverse's codegen.

[overlookmotel]

@DonIsaac Rzvxa is the master of the codegen, but is off radar at the moment, and I'm not sure when I'd get to it. You comfortable enough with oxc_ast_tools to implement yourself?

[DonIsaac]

I'm not very comfortable, but I can take a look and try it out.

[overlookmotel]

Implemented in #6350. Thanks Don!