[wasm] Unmanaged structs are considered blittable if module has `DisableRuntimeMarshallingAttribute` (#73310)

* [wasm] Unmanaged structs are considered blittable if module has DisableRuntimeMarshallingAttribute.
* Look for the DisableRuntimeMarshallingAttribute on the assembly where pinvoke method is declared.
- Cache DisableRuntimeMarshallingAttribute on assembly.
- Test without DisableRuntimeMarshallingAttribute.
* WasmBuildNative only without AOT.
* Unit test with struct in different assembly.

* Update, and add some additional tests
* [wasm] PInvokeTableGenerator: Avoid crash when processing unmanaged
callbacks with function pointers.
Co-authored-by: NAnkit Jain <radical@gmail.com>