[naga hlsl-out] Handle array types for function return values and calls

[jamienicol]

Connections
Fixes #4393

Description
Currently the HLSL backend omits the array part of return types for functions and function call statements. This adds it in. Curiously it appears DXC allows the [n] part to follow the function name, like so:

float my_fun()[3] {...}

but FXC does not allow this. However, both FXC and DXC work if we use a typedef:

typedef float my_array[3];
my_array my_fun() {...}

Which is easy enough, so we do this.

Testing
Enabled the array-in-function-return-type test for the HLSL backend. Also extended it to use nested arrays to ensure those work as expected.

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
  • --target wasm32-unknown-emscripten
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.

[teoxoy]

Nice!