[MC][WebAssembly] Allow strings for import modules and names in asm (#182896)
Current tooling for the WebAssembly component model uses import modules
and names such as `$root` and `[thread-index]`. Importing these from
assembly files requires support for non-valid identifiers in
`.import_name` and `.import_module` directives. This PR adds support for
specifying those as strings, e.g.:
```asm
.import_module __wasm_component_model_builtin_thread_index, "$root"
.import_name __wasm_component_model_builtin_thread_index, "[thread-index]"
```