IR support for switch instructions

[vaivaswatha]

Description

This PR adds a new IR instruction switch, that supports both exhaustive (for exhaustive matchs, verified by the front-end) and non-exhaustive switches.

Since matchs in the frontend still translate to an if-else ladder, a switch is never generated yet. So for testing, I've added support in the test harness to compile and execute (in the VM) sway-ir files directly.

[codspeed-hq]

Merging this PR will not alter performance

✅ 25 untouched benchmarks

---

_{Comparing vaivaswatha/ir_switch (9988e37) with master (0d8fbc8)}

[cursor]

PR Summary

Medium Risk
Touches core IR semantics and Fuel backend lowering (including data-section encoding), which can affect codegen correctness; EVM support is stubbed (todo!()), reducing scope but requiring care to avoid accidental execution paths.

Overview
Adds a new switch terminator to sway-ir (parser/printer, block successor handling, verifier errors + validation rules, and multiple optimization/analysis passes) and wires it through Fuel backend codegen.

Fuel asm generation now lowers switch via a jump-table style OrganizationalOp::Switch, including new data-section support for WordArray entries (byte emission, display/debug printing, size accounting, and constant-prop/basic-block boundary updates). EVM codegen is plumbed to recognize switch but the lowering is still todo!().

Testing is extended with an ir_run e2e category that compiles and executes main.ir directly via new forc_pkg::compile_ir, plus new IR switch test programs and CFG simplification tests.

^{Written by Cursor Bugbot for commit 9988e37. This will update automatically on new commits. Configure here.}

[fuel-cla-bot]

Thanks for the contribution! It looks like @vaivaswatha is an internal user so signing the CLA is not required. However, they are not a member of this GitHub org so we can't confirm this.

[fuel-cla-bot]

Thanks for the contribution! Unfortunately we can't verify the commit author(s): Vaivaswatha Nagaraj <v***@f***.sh> Vaivaswatha N <v***@f***.sh>. One possible solution is to add that email to your GitHub account. Alternatively you can change your commits to another email and force push the change. After getting your commits associated with your GitHub account, refresh the status of this Pull Request.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with Cloud Agents, enable Autofix in the Cursor dashboard.}

[cursor]

In-place SUBI corrupts discriminant register for successor blocks

High Severity

The SUBI writes the adjusted discriminant back into discrim_reg, the same virtual register returned by value_to_register(discriminant). This register is shared by all uses of that IR value. If any successor block references the discriminant directly (not via phi/block arguments), value_to_register returns the same register, and the successor sees the subtracted value instead of the original. A fresh temporary register from self.reg_seqr.next() is needed for the adjusted value.