[libc][NFC] Rename RPC opcodes to better reflect their usage

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

[libc] Remove dependency on `cpp::function` in `rpc.h` (#112422)

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`. Befo

[libc] Remove dependency on `cpp::function` in `rpc.h` (#112422)

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.

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[libc] Implement the 'rename' function on the GPU (#109814)

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