This is the first step in preparation for:
https://discourse.llvm.org/t/rfc-make-clang-builtin-math-functions-constexpr-with-llvm-libc-to-support-c-23-constexpr-math-functions/86450

The GPU stdio functions were depending on indirect inclusion for some of
their dependencies. This patch should fix all of that.

Summary:
RPC_ is a generic prefix here, use LIBC_ to indicate that these are
opcodes used to implement the C library

Summary:
Currently, the RPC interface uses a basic opcode to communicate with the
server. This currently is 16 bits. There's no reason for this to be 16
bits, because on the GPU a 32-bit write is the same as a 16-bit write
performance wise.

Additionally, I am now making all the `libc` based opcodes qualified
with the 'c' type, mimiciing how Linux handles `ioctls` all coming from
the same driver. This will make it easier to extend the interface when
it's exported directly.

Summary:
These are provided by a resource header now, cut these from the
dependencies and only provide the ones we use for RPC.

Summary:
There are a few of these leftover, they should all use the
`LIBC_NAMESPACE_DECL` version because that implies visibility.

Summary:
I'm going to attempt to move the `rpc.h` header to a separate folder
that we can install and include outside of `libc`. Before doing this I'm
going to try to trim up the file so there's not as many things I need to
copy to make it work. This dependency on `cpp::functional` is a low
hanging fruit. I only did it so that I could overload the argument of
the work function so that passing the id was optional in the lambda,
that's not a *huge* deal and it makes it more explicit I suppose.

https://github.com/llvm/llvm-project/issues/60481

Summary:
Straightforward implementation like the other `stdio.h` functions.