MIR restructuring and fixes

[sbillig]

• all expression lowering now happens in mir
• copied the BodyBuilder pattern from v1 MIR, to replace the bug-prone needs_block_aware_lowering logic, and returning the "next block"
• moved evm-specific things from mir into codegen
• canonicalize_zero_sized rewrites zero-sized type operations to unit, and removes dead stores
• moved/improved mir printing from fe check into mir crate, added some mir snapshot tests

Things I ran into and fixed along the way:

• parser stricter about method call syntax (opening paren must be on same line)
• parser stricter about < as generic arg list vs comparison
• fixed type checking of comparisons involving unknown int types
• fixed resolution of trait methods in mir

Sorry about the mega commit; there was a lot of wip churn in the mir structure/lowering and codegen that I squashed together. Half of the line changes are snapshots; it's not as bad as it looks :)

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[Copilot]

Pull request overview

This PR restructures the MIR (Mid-level Intermediate Representation) system with several key improvements:

• Introduces the BodyBuilder pattern (from v1 MIR) to replace bug-prone block-aware lowering logic
• Moves all expression lowering into MIR (previously split between HIR and MIR)
• Adds new MIR transformations including canonicalize_zero_sized for ZST handling and insert_temp_binds for value binding
• Moves EVM-specific logic from MIR into codegen
• Improves MIR printing with a new formatting module
• Makes parser stricter about method call syntax and generic argument disambiguation

The majority of line changes are snapshot tests reflecting the new MIR structure.

Reviewed changes

Copilot reviewed 148 out of 149 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
library/std/src/abi/sol.fe	Introduces temporary locals to fix evaluation order issues in write_word and finish methods
crates/mir/src/ir.rs	Restructures core MIR types with new Rvalue enum, TerminatingCall, and LocalId-based system
crates/mir/src/ir/body_builder.rs	Adds new BodyBuilder helper for constructing MIR bodies with current block tracking
crates/mir/src/transform.rs	New module with insert_temp_binds and canonicalize_zero_sized transformation passes
crates/mir/src/lower/mod.rs	Major refactoring of expression lowering to use BodyBuilder pattern
crates/mir/src/lower/expr.rs	Complete rewrite of expression lowering without "next block" return pattern
crates/mir/src/lower/aggregates.rs	Simplified aggregate lowering using InitAggregate instruction
crates/mir/src/fmt.rs	New MIR pretty-printing module for debugging and testing
crates/parser/src/parser/expr.rs	Makes parser stricter about method call syntax (opening paren on same line)
crates/parser/src/parser/path.rs	Improves disambiguation between generic args and comparison operators

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[cburgdorf]

Great work!