(fix): make pipeline pickleable #72

Job	Run time
build sdist	25s
build on linux (x86_64 - 2_28)	3m 34s
build on linux (aarch64 - 2_28)	3m 33s
build on macos (x86_64)	2m 13s
build on macos (aarch64)	2m 34s
build on windows (x86_64)	11m 3s
build on windows (aarch64)	12m 57s
build on linux (armv7 - 2_28)	3m 42s
build on linux (ppc64le - 2_28)	3m 28s
build on linux (x86_64 - musllinux_1_2)	3m 22s
build on linux (aarch64 - musllinux_1_2)	3m 58s
build on linux (armv7 - musllinux_1_2)	3m 29s
build on windows (i686)	11m 32s
inspect	4s
version	0s
publish	0s
	1h 5m 54s

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