Replace Win32 PAL implementation with minipal implementation

[AaronRobinsonMSFT]

This PR removes the PAL Win32 emulation of CRITICAL_SECTION. The emulation logic is unnecessarily complicated and used both a pthread mutex and condition variable. For CoreCLR purposes a mutex is sufficient.

A new minipal API was introduced, minipal_critsect. This uses the Win32 CRITICAL_SECTION on the Windows platform and pthread_mutex_t on all other platforms. This implementation aligns with a private "critical section" defined for the GC and native AOT. All now use this new API.

The CRITICAL_SECTION associated APIs and tests in the CoreCLR PAL have been removed.

[huoyaoyuan]

FWIW, I tested std::mutex and mtx_t on Windows. std::mutex is about the same speed of CRITICAL_SECTION, and mtx_t is 2x slower. We are unable to use std::mutex because it's not noexcept.

[AaronRobinsonMSFT]

FWIW, I tested std::mutex and mtx_t on Windows. std::mutex is about the same speed of CRITICAL_SECTION, and mtx_t is 2x slower. We are unable to use std::mutex because it's not noexcept.

It isn't just because of noexcept. On Windows std::mutex will pull in the concrt, which is a huge dependency.

mtx_t

clang on macOS doesn't support C11 threads. It isn't an option in any case.