Migrate from doc_auto_cfg to doc_cfg #380

Job	Run time
set-msrv / set-msrv	4s
macos (stable)	40s
linux (x86_64-unknown-linux-gnu, stable)	32s
macos (1.85.0)	45s
linux (x86_64-unknown-linux-gnu, 1.85.0)	36s
windows (x86_64-pc-windows-gnu, stable)	1m 2s
build (1.85.0, wasm32-unknown-unknown)	26s
windows (x86_64-pc-windows-gnu, 1.85.0)	1m 35s
build (1.85.0, loongarch64-unknown-linux-gnu)	29s
build (stable, wasm32-unknown-unknown)	23s
build (stable, thumbv7em-none-eabi)	22s
cross (stable, aarch64-unknown-linux-gnu, default)	49s
cross (1.85.0, powerpc-unknown-linux-gnu, default)	47s
cross (1.85.0, aarch64-unknown-linux-gnu, default)	59s
cross (stable, powerpc-unknown-linux-gnu, default)	53s
build (stable, loongarch64-unknown-linux-gnu)	31s
build (1.85.0, thumbv7em-none-eabi)	23s
	11m 16s

Provide feedback