Update wgpu to 0.18

[JacobMillward]

This allows the latest version of egui to be used. Required updating several RenderPassDescriptor objects to account for new fields, as well as updating to handle the new texture format Rgb10a2Uint.

Also updated the minimal-egui example.

[parasyte]

@JacobMillward Heads up, there are CI failures that need to be fixed. It's the dependency chain for imgui. which needs https://github.com/Yatekii/imgui-wgpu-rs/pull/104. I would accept this with a git dependency reference for imgui-wgpu pointing at the git rev in that PR. I can't say it will be the last CI failure, though.

[JacobMillward]

Superseded by #391