Change raw funcref/externref from nuint to IntPtr

[kpreisser]

Adapt to changes in bytecodealliance/wasmtime#6338, which changes the type of raw funcrefs/externrefs from usize to void*.

Therefore we change nuint to IntPtr for these types, which although technically equivalent (except for the signed/unsigned behavior), better matches the native API.

[peterhuene]

Thanks for fixing this! Will merge once the CI rerun passes.

[peterhuene]

Ye ol' CI artifact download flakiness is back, it seems.

[peterhuene]

I'm going to merge given the CI failure appears to be due to GitHub flakiness and not a result of these changes.

[peterhuene]

On a side note: the MSBuild folks fixed this particular error as to not eat the inner exception's context, so hopefully we'll get to the bottom of the flakiness with an updated .NET SDK (eventually).

[kpreisser]

On a side note: the MSBuild folks fixed this particular error as to not eat the inner exception's context, so hopefully we'll get to the bottom of the flakiness with an updated .NET SDK (eventually).

Note that starting with CI build 1819, MSBuild/VS was updated to 17.6, which now includes the inner exception message in the error message:

  Downloading from "https://github.com/bytecodealliance/wasmtime/releases/download/dev/wasmtime-dev-x86_64-linux-c-api.tar.xz" to "D:\a\wasmtime-dotnet\wasmtime-dotnet\src\obj\wasmtime-dev-x86_64-linux-c-api.tar.xz" (13,069,756 bytes).
  Downloading from "https://github.com/bytecodealliance/wasmtime/releases/download/dev/wasmtime-dev-aarch64-linux-c-api.tar.xz" to "D:\a\wasmtime-dotnet\wasmtime-dotnet\src\obj\wasmtime-dev-aarch64-linux-c-api.tar.xz" (13,156,200 bytes).
D:\a\wasmtime-dotnet\wasmtime-dotnet\src\Wasmtime.csproj(151,5): error MSB3923: Failed to download file "https://github.com/bytecodealliance/wasmtime/releases/download/dev/wasmtime-dev-x86_64-macos-c-api.tar.xz".  Authentication failed, see inner exception. ---> The Local Security Authority cannot be contacted
Error: Process completed with exit code 1.

Unfortunately, I'm also not sure what the error The Local Security Authority cannot be contacted means here exactly. It might be some random connection/network issue, as in this run two downloads succeded but the third one failed, but unfortunately that exception doesn't seem to be retriable (#222).

[peterhuene]

I started a discussion to see if the GitHub folks can help us out.