Dash fixes and pthreads

[john-sharratt]

This merge brings in support for pthreads using the WASI threads spec and fixes a number of issues with dash WASIX

[john-sharratt]

Note the snapshot tests won't work until I regenerate them all - which I'll do now but be aware they are not backwards compatible

[theduke]

Mostly looks good to me, apart from some smaller requests and one larger issue (Errno).

[john-sharratt]

Note the snapshot tests won't work until I regenerate them all - which I'll do now but be aware they are not backwards compatible

Snapshot tests are updated but there is a strange cranelift error that is not understood

---
source: tests/integration/cli/tests/snapshot.rs
assertion_line: 268
expression: snapshot
---
{
  "spec": {
    "name": null,
    "wasm_hash": "3d1ec94e88031b45f7f6d4213f045060",
    "use_packages": [],
    "cli_args": [],
    "stdin": null,
    "debug_output": true,
    "enable_threads": true
  },
  "result": {
    "Success": {
      "stdout": "",
      "stderr": "error: failed to run `/tmp/wasmer-snapshot-tests/3d1ec94e88031b45f7f6d4213f045060.wasm`\n│   1: module instantiation failed (compiler: cranelift)\n╰─▶ 2: Validation error: Invalid type (at offset 165)\n",
      "exit_code": 1
    }
  }
}