[Stack Switching] Align switch/resume_throw result typing with spec

[byeongjee]

Align switch/resume_throw result typing with stack-switching spec

Problem

Current wasmstack op surface models switch and resume_throw as producing no normal results. This blocks representation of valid typed result-flow forms described by the official typing rules.

Why this matters

Spec-conformant programs requiring result propagation through switch/resume_throw cannot be represented or validated in the current IR.

Repro

• Test: test/wasmstack/spec-gap-switch-resume-throw-results.mlir (currently XFAIL)
• Parser/op model rejects SSA-result forms.

Expected behavior

switch and resume_throw should support typed results where permitted by continuation/tag typing rules.

Suggested implementation direction

1. Update ODS for wasmstack.switch and wasmstack.resume_throw result modeling.
2. Update verifier stack-effect rules and typing checks.
3. Update emitter stack assumptions and binary encoding logic.
4. Add conversion coverage from WAMI forms.

Acceptance criteria

• test/wasmstack/spec-gap-switch-resume-throw-results.mlir flipped from XFAIL to passing.
• No regressions in existing stack-switching verify/emission suites.