[wasm] Fix typedef for non-void interp entry callbacks

[lambdageek]

For UnmanagedCallersOnly methods that return non-void, pass the address of the
return variable to the interp entry method.

[ghost]

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Issue Details

---

For UnmanagedCallersOnly methods that return non-void, pass the address of the
return variable to the interp entry method.

Author:	lambdageek
Assignees:	-
Labels:	arch-wasm, area-Interop-mono
Milestone:	-

[lambdageek]

Should we backport to 6.0? @lewing

[lambdageek]

Previously it was generating something like this:

typedef void  (*WasmInterpEntrySig_0) (int,int*,int*,int*,int*,int*,int*,int*);
int wasm_native_to_interp_System_Private_CoreLib_ComponentActivator_LoadAssemblyAndGetFunctionPointer (int arg0,int arg1,int arg2,int arg3,int arg4,int arg5) { 
int res;
((WasmInterpEntrySig_0)wasm_native_to_interp_ftndescs [0].func) (&res, &arg0, &arg1, &arg2, &arg3, &arg4, &arg5, wasm_native_to_interp_ftndescs [0].arg);
return res;
}

for

[UnmanagedCallersOnly]
public static unsafe int LoadAssemblyAndGetFunctionPointer(IntPtr assemblyPathNative, IntPtr typeNameNative, IntPtr methodNameNative, IntPtr delegateTypeNative, IntPtr reserved, IntPtr functionHandle)

[lambdageek]

/backport to release/6.0

[github-actions]

Started backporting to release/6.0: https://github.com/dotnet/runtime/actions/runs/1308006447