Rust

`egui_extras`: Make `serde` an opt-in feature #11647

Job	Run time
android	40s
Check wasm32 + wasm-bindgen	2m 33s
Format + check + test	6m 34s
Check Windows	2m 46s
cargo-deny aarch64-apple-darwin	41s
cargo-deny aarch64-linux-android	39s
cargo-deny i686-pc-windows-gnu	40s
cargo-deny i686-pc-windows-msvc	38s
cargo-deny i686-unknown-linux-gnu	39s
cargo-deny wasm32-unknown-unknown	41s
cargo-deny x86_64-apple-darwin	39s
cargo-deny x86_64-pc-windows-gnu	38s
cargo-deny x86_64-pc-windows-msvc	43s
cargo-deny x86_64-unknown-linux-gnu	39s
cargo-deny x86_64-unknown-linux-musl	41s
cargo-deny x86_64-unknown-redox	41s
	20m 32s

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