[wgpu] Expose wgpu::Adapter via RenderState (#2954)

* [wgpu] Expose adapter, better errors, better docs, more code sharing, use stencil bits

* doc fix

* remove unnecessary unsafe

* handle missing framebuffer format

* better handling of renderstate creation in winit.rs

* remove unnecessary use directive

crates/eframe/Cargo.toml

@@ -80,7 +80,7 @@ egui = { version = "0.21.0", path = "../egui", default-features = false, feature
   "log",
 ] }
 log = { version = "0.4", features = ["std"] }
-thiserror = "1.0.37"
+thiserror.workspace = true
 
 #! ### Optional dependencies
 ## Enable this when generating docs.