Fix mingw-w64 GCC toolchain compatibility issues

[eramongodb]

This PR fixes and improves libmongocrypt compatibility with the mingw-w64 GCC toolchain (referred to as just "mingw" going forward for brevity) to unblock upcoming changes to downstream mingw task coverage improvements in the C and C++ drivers.

---

The first issue is with libbson compatibility:

 error: #error "__USE_MINGW_ANSI_STDIO > 0 is required for correct PRI* macros"
   27 | #error "__USE_MINGW_ANSI_STDIO > 0 is required for correct PRI* macros"
      |  ^~~~~

This is an old mingw compatibility problem that is well-described by this comment concerning format string tests:

The test failure appears if you compile for the target platform MINGW64 or MINGW32 which uses the old Microsoft C standard library called "msvcrt" which is C89 and also uses some MinGW functions that implement some C99 functionality. strftime is part of msvcrt which means it conforms only to C89 and it does not have the new conversion specifiers like %G or %g. The fix is to upgrade to MinGW+UCRT and just use the new C standard library which properly conforms to new standards.

Upgrading to a UCRT-based mingw-w64 toolchain is beyond the scope of this PR (although we should investigate doing so properly; filed DEVPROD-20813 in advance to prepare EVG Windows distros for such a transition). For now, given this mingw workaround applies to the entire codebase (not just libbson), a call to add_compile_definitions() is added to the root CMakeLists.txt that defines __USE_MINGW_ANSI_STDIO=1 for the entire project when CMake detects a MINGW compiler is being used.

---

The second issue is with calls to BCrypt* API:

error: passing argument 9 of 'BCryptEncrypt' from incompatible pointer type [-Werror=incompatible-pointer-types]
      |                               args.bytes_written,
      |                               ~~~~^~~~~~~~~~~~~~
      |                                   |
      |                                   uint32_t * {aka unsigned int *}
note: expected 'ULONG *' {aka 'long unsigned int *'} but argument is of type 'uint32_t *' {aka 'unsigned int *'}

The platform-independent struct aes_256_args_t contains a uint32_t *bytes_written pointer, where uint32_t is an unsigned int. This pointer type is incompatible with mingw where ULONG is defined as unsigned long. Therefore, a ULONG bytes_written local variable is used to obtain a valid pointer to ULONG (guarded by args.bytes_written != nullptr).

---

The third issue is related to the __USE_MINGW_ANSI_STDIO problem above:

warning: unknown conversion type character 'z' in format [-Wformat=]
      |       kms_request_str_appendf (v, "%zu", request->payload->len);
      |                                     ^

It seems __attribute__((format(__printf__, ...))) is not aware of __USE_MINGW_ANSI_STDIO=1 and uses the MSVCRT-compatible (non-C99-conforming) printf mingw definition rather than a C99-conforming definition. These warnings are addressed by using gnu_printf rather than __printf__ (or printf) when building with GCC, as currently done in mongo-c-driver (the GCC version check is omitted, as I do not believe we are, or want to, continue supporting such old GCC versions).

[kevinAlbs]

LGTM! Thank you for investigating and the fix.