Convert CoreCLR classic debug logging to use the minipal mutex

[jkoritzinsky]

Removes another usage of the CoreCLR Win32 PAL Mutex

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[Copilot]

Pull Request Overview

This PR replaces the CoreCLR Win32 PAL HANDLE–based logging mutex with the cross-platform minipal_mutex.

• Changed the global LogFileMutex type from HANDLE to minipal_mutex*.
• Updated EnterLogLock/LeaveLogLock to call minipal_mutex_enter/minipal_mutex_leave.
• Modified InitializeLogging to new and initialize a minipal_mutex, using InterlockedCompareExchangeT to install it.

Comments suppressed due to low confidence (1)

src/coreclr/utilcode/log.cpp:184

• [nitpick] The local variable name 'mutex' is very generic and could be confused with the global 'LogFileMutex'. Consider renaming it to 'newLogFileMutex' or similar for clarity.

    minipal_mutex* mutex = new minipal_mutex;

[jkoritzinsky]

/ba-g failures are unrelated