Remove Windows, Mac and Snap build files

[ataffanel]

We have taken the decision to stop trying to build a Windows and Mac client as well as the Snap package. The client is still going to be fully supported to run on Windows, Mac and Linux using a user-installed python but we are not going to build a .exe for Windows, an .app for Mac or a Snap for Ubuntu.

This is done because of the difficulty to build, test and maintain a workable build. The status quo is that there has not been a workable client build for at least a year now (see #272 ,#460 ,#229 ,#566). We also think that most Crazyflie user will have use for a python installation on their system.

If anyone is interested in contributing a Windows, Mac, or any other platform build (Snap, Flatpak, ...) we will gladly reconsider.