Rewrite to allow GCC Compilation on Windows

[ZaneL]

Hello,

I'm using CMAKE to build your library and link it into my project. In Windows, if I use MSVC, it works fine. Out of curiosity, I tried to use G++ (mingw) on Windows and I encountered a few problems.

For some reason, these lines were being overridden by simpleble's CMAKE files, and it kept reverting back to an earlier C++ standard that doesn't have co-routine support. As a result, the winrt header files wouldn't compile.

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

I added this line which fixed the problem target_compile_features(simpleble PUBLIC cxx_std_20)

Then some compilation errors started popping up, for example, I had to change this

GattDescriptor PeripheralBase::_fetch_descriptor(const BluetoothUUID& service_uuid, const BluetoothUUID& characteristic_uuid, const BluetoothUUID& descriptor_uuid);

To this GattDescriptor _fetch_descriptor(const BluetoothUUID& service_uuid, const BluetoothUUID& characteristic_uuid, const BluetoothUUID& descriptor_uuid);

And I had to add const in a few places like this:

Here-->for (const auto& service_guid : service_data) {
                std::string service_uuid = guid_to_uuid(service_guid);
                data.service_data.emplace(std::make_pair(service_uuid, ByteArray()));
             }

Then I encountered more problems because "roapi.h" was being included, and there are MSVC specific compiler macros that are needed to get this thing to build

#pragma region Desktop Family
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
    RO_INIT_SINGLETHREADED     = 0,      // Single-threaded application
#endif // WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
    RO_INIT_MULTITHREADED      = 1,      // COM calls objects on any thread.
} RO_INIT_TYPE;

Anyway, I think this project could build with mingw on windows if some stuff was modified a bit. Just wondering what your thoughts are...