[Request] Remove WGPU as default feature

[Adam-Cosner]

As the title says. WGPU is intended for high graphical demand applications and currently libcosmic uses WGPU but explicitly disables the discrete GPU, resulting in libcosmic apps that use WGPU using the integrated GPU. Because of this, resizing is very choppy as it has to reallocate the surface every frame that it's resized. When I tested on my own machine and disabled WGPU, the app performed pretty much the same but the choppy resizing was completely eradicated.