Release k12 v0.4.0 #1527

Job	Run time
minimal-versions / minimal-versions	25s
set-msrv / set-msrv	6s
test (stable)	26s
test (1.85.0)	25s
build (1.85.0, wasm32-unknown-unknown)	25s
build (stable, thumbv7em-none-eabi)	20s
build (stable, wasm32-unknown-unknown)	25s
build (1.85.0, thumbv7em-none-eabi)	18s
	2m 50s

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