Add semi-additive categories infrastructure #3917

Job	Run time
build (supported)	3m 44s
build (latest)	3m 48s
nix	2m 10s
build (dev, --warnings)	3m 22s
quick-build (supported, ubuntu-latest)	3m 27s
quick-build (latest, ubuntu-latest)	3m 25s
opam-build (supported, ubuntu-latest)	4m 39s
quick-build (dev, ubuntu-latest)	3m 22s
opam-build (latest, ubuntu-latest)	4m 45s
opam-build (dev, ubuntu-latest)	4m 18s
doc-dep-graphs	9m 27s
doc-alectryon	15m 21s
doc-coqdoc	1m 34s
doc-timing	1m 45s
coqchk (dev)	2m 4s
coqchk (latest)	2m 10s
coqchk (supported)	2m 0s
install (latest)	1m 48s
install (dev)	1m 48s
install (supported)	1m 50s
delete-artifacts	10s
deploy-doc	0s
	1h 16m 57s

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