Migrate from `doc_auto_cfg` to `doc_cfg` (#740) #557

Job	Run time
minimal-versions / minimal-versions	43s
set-msrv / set-msrv	4s
test (1.85.0)	35s
test (stable)	29s
build (1.85.0, wasm32-unknown-unknown)	24s
build (stable, thumbv7em-none-eabi)	20s
build (1.85.0, thumbv7em-none-eabi)	21s
build (stable, wasm32-unknown-unknown)	22s
	3m 18s

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