This change adds a basic coredump generation after a WebAssembly trap
was entered. The coredump includes rudimentary stack / process debugging
information.
A new CLI argument is added to enable coredump generation:
```
wasmtime --coredump-on-trap=/path/to/coredump/file module.wasm
```
See ./docs/examples-coredump.md for a working example.
Refs https://github.com/bytecodealliance/wasmtime/issues/5732
