Remove CLOCK_PROCESS_CPUTIME_ID/CLOCK_THREAD_CPUTIME_ID

[TerrorJack]

After WebAssembly/WASI#197 has landed, CLOCK_PROCESS_CPUTIME_ID/CLOCK_THREAD_CPUTIME_ID are invalid in recent versions of wasmtime/uvwasi, even if targetting wasi snapshot 1. This leads to runtime error, so I propose we do something about it:

• Remove these two from wasi-libc altogether
• Alias to CLOCK_MONOTONIC to make it sort of work

[sunfishcode]

I agree. Aliasing the process-oriented clock IDs to CLOCK_MONOTONIC would make sense to do under the _WASI_EMULATED_PROCESS_CLOCKS flag, which is already emulating some of the process-oriented clock features in terms of CLOCK_MONOTONIC.

[brettcannon]

Can this be removed now? python/cpython#115714 stumbled across this causing incorrect results.