Closes #161461
- This is my first time contributing to libc's POSIX, so for reference I
used `clock_gettime` implementation for Linux. For convenience, here is
the description of `clock_settime` function
[behavior](https://www.man7.org/linux/man-pages/man3/clock_settime.3.html)

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

This reverts commit 0adff0af20c7d9bae8bd8bdf402506c10369ead1.

Breaks the GPU build

Add a `clock_gettime` emulation layer and use it to implement the `time`
entrypoint.

For windows, the monotonic clock is emulated using `QPC`.
The realtime clock is emulated using `GetSystemTimePreciseAsFileTime`.

This is a part of #97655.

Reverts llvm/llvm-project#98075

bots are broken

This is a part of #97655.

Reverts llvm/llvm-project#91657 and Relands #91485

Reverts llvm/llvm-project#91485. It breaks GPU and fuchisa.