Remove VirtualAlloc & VirtualFree from standard library + update std.heap.PageAllocator

[ziggoon]

This commit removes the VirtualAlloc and VirtualFree definitions from the standard library as outlined in #22846.

Additionally, a slight refactor has been made to the Windows implementation of std.heap.PageAllocator to check for page_size_min as follow-up to #23097.

[e4m2]

This seems worth it to do, just to make sure we don't lose any functionality here. VirtualFree() is basically (without error handling minutiae) this:

BOOL __stdcall VirtualFree(LPVOID lpAddress, SIZE_T dwSize, DWORD dwFreeType)
{
    PVOID BaseAddress = lpAddress;
    ULONG_PTR RegionSize = dwSize;
    
    NTSTATUS Status = NtFreeVirtualMemory(NtCurrentProcess(), &BaseAddress, &RegionSize, dwFreeType);
    if (Status == STATUS_INVALID_PAGE_PROTECTION) {
        if (!RtlFlushSecureMemoryCache(BaseAddress, RegionSize)) {
            return FALSE;
        }

        Status = NtFreeVirtualMemory(NtCurrentProcess(), &BaseAddress, &RegionSize, dwFreeType);
    }

    return NT_SUCCESS(Status);
}