Rust

Add `egui_kittest`, a test harness for egui #12863

Job	Run time
android	35s
Check wasm32 + wasm-bindgen	2m 40s
Check wasm32+atomics	1m 35s
cargo-deny aarch64-apple-darwin	39s
Format + check + test	31s
ios	40s
cargo-deny aarch64-linux-android	38s
cargo-deny i686-pc-windows-gnu	42s
Check Windows	1m 37s
cargo-deny i686-pc-windows-msvc	38s
cargo-deny i686-unknown-linux-gnu	39s
cargo-deny wasm32-unknown-unknown	40s
cargo-deny x86_64-apple-darwin	41s
cargo-deny x86_64-pc-windows-gnu	42s
cargo-deny x86_64-pc-windows-msvc	38s
cargo-deny x86_64-unknown-linux-gnu	39s
cargo-deny x86_64-unknown-linux-musl	41s
cargo-deny x86_64-unknown-redox	37s
	15m 32s

Provide feedback