[Wasm-GC] Local init tracking should track unreachable local.set too

[Asumu Takikawa]

Example test cases:

```
//@ runWebAssemblySuite("--useWebAssemblyTypedFunctionReferences=true", "--useWebAssemblyGC=true")

import * as assert from "../assert.js";
import { compile } from "./wast-wrapper.js";

function testUnreachable()
{
  // A local.set in unreachable code should still count for init.
  compile(`
    (module
      (type (struct))
      (func (local (ref 0))
        (unreachable)
        (local.set 0 (struct.new 0))
        (local.get 0)
        drop))
  `);

  compile(`
    (module
      (type (struct))
      (func (local (ref 0))
        (unreachable)
        (local.tee 0 (struct.new 0))
        drop
        (local.get 0)
        drop))
  `);
}

testUnreachable()
```

These currently fail but should validate.

[Asumu Takikawa]

Pull request: https://github.com/WebKit/WebKit/pull/21555

[EWS]

Committed 271910@main (025c31d1220e): <https://commits.webkit.org/271910@main>

Reviewed commits have been landed. Closing PR #21555 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/119533296>