Handle integer overflow/underflow for non-64-bit integers

[anton-trunov]

fixes #4646

Description

This PR fixes the linked issue by introducing overflow/underflow checks in the Add, Mul, Sub stdlib traits implementations for the u8, u16 and u32 types.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[vaivaswatha]

We'll probably need to do something about const_eval too

sway/sway-core/src/ir_generation/const_eval.rs

Line 527 in 48f7125

match intrinsic.kind {

The corresponding tests are in should_pass/language/const_inits.

[IGI-111]

Yeah we probably need something for the const evaluations too.

Are you sure there are no missing operators, what about left shift?

[anton-trunov]

We'll probably need to do something about const_eval too

Noted, will add, thanks.

Are you sure there are no missing operators, what about left shift?

Yeah, I was going to go over the logical operations as well, probably in a separate PR if any changes are required there, but it also makes sense to do it here in one go.

[anton-trunov]

Ok, const_eval seems to be done. To handle const_eval, I had to cover more Sway features in it: we can now evaluate functions with bodies of length more than one and we also process let-expressions and local consts, including tracking variable scopes in code blocks.

[IGI-111]

LGTM, but I think the logical operators should also be in this PR if necessary.

This makes me think we might want to add const fn as a language construct eventually.