codegen optimization: constant expression folding

[Dentosal]

Description

Follow-up to #7109. Adds support to propagating and folding expressions in the fuel-vm codegen stage.

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).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• 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.

[codspeed-hq]

CodSpeed Performance Report

Merging #7149 will not alter performance

_{Comparing dento/asm-gen-opt-2 (a762ce1) with master (a428376)}

Summary

✅ 23 untouched benchmarks

[Dentosal]

With these optimizations enalbed, it's possible to hit a pre-existing bug which causes compiler panic. The should_fail/arith_overflow/u64_mul_overflow test from (cargo run --locked --bin test -- --locked --release) hits this. The multiplication in const_indexing_aggregates_function overflows, and compiler panics:

sway/sway-core/src/asm_generation/fuel/optimizations/const_indexed_aggregates.rs

Line 118 in 5a95c65

.insert(dest.clone(), RegContents::Constant(c1 * c2));