Rename `WidgetArena::widget_states` to `WidgetArena::states` #2536

Job	Run time
formatting	38s
cargo clippy (windows-latest)	4m 34s
cargo clippy (macos-latest)	2m 36s
cargo check (msrv) (windows-latest)	1m 41s
cargo check (msrv) (wasm32)	21s
cargo clippy (ubuntu-latest)	3m 27s
cargo check (aarch64-android)	25s
cargo check (msrv) (macos-latest)	42s
cargo check (msrv) (ubuntu-latest)	38s
cargo clippy (wasm32)	1m 57s
cargo doc	45s
Prime LFS Cache	7s
cargo test (wasm32)	19s
typos	6s
cargo test (windows-latest)	3m 9s
cargo test (macos-latest)	1m 36s
cargo test (ubuntu-latest)	3m 13s
	26m 14s

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