Add Delimiter tokens to the parser

[eureka-cpu]

Main issue is #5140
Adds Delimiter tokens, and updates their corresponding use cases.

Ref #3634 #3734
Closes #3635
Closes #3594

[mohammadfawaz]

Looks good! But you have some E2E test failures that need to be addressed. Specifically, test.toml for:

    should_fail/trait_method_signature_mismatch ... failed
    should_fail/abi_method_signature_mismatch ... failed

should be updated.

[mohammadfawaz]

Ok so I will write my thoughts on the failing test here:
for trait_method_signature_mismatch, we used to emit the following error:

Now, we just emit this (not pointing to any location):

We previously used to point to the function span itself because the return type is missing (i.e. () implicitly). Now that we’re using Span::dummy(), the error is different and doesn’t point to anything which is not good. I thought we didn’t need this span for anything but clearly we do.
So I looked at what Rust does… it seems to point to the span of the following character as in:

So I suggest we do the same instead of returning a dummy span.

[JoshuaBatty]

Can we add a doc comment outining what this Span is pointing to when we have an implicit return type.

[eureka-cpu]

Putting this on hold while I work on FuelLabs/fuelup#457 for the next beta release.

[sdankel]

We should rethink this solution in light of #4981

[eureka-cpu]

We should rethink this solution in light of #4981

In this instance, we don't want the span to be none since it would mean that we couldn't point to where the error actually happens

Side note: this problem actually occurred due to essentially a similar implementation of #4981 where the return type could be None and we were replacing the span of what would be the return type span with the span of the entire function signature. In my main comment you can see what Rust does and how this PR aims to achieve that.

[eureka-cpu]

Closing due to how big of a PR this became, and I no longer have time to try and finish it. There is some good stuff in here, for anyone who may decide to tackle the issue of adding delimiters to the parser and how that could affect the resulting AST, error handling and so on.