[clang] Adding `asuint` implementation to hlsl (PR #107292)

[Justin Bogner via cfe-commits]

https://github.com/bogner commented:

This is going in the right direction but the tests need some work. I made a couple of comments to point you in the right direction.

We also need to make sure we're testing all of the cases we care about, so we need tests with inputs of `int`, `uint`, vector of `int`, vector of `uint`, `float`, vector of `float`. You've covered some but not all of these.

https://github.com/llvm/llvm-project/pull/107292