Add semi-additive categories infrastructure #3916

Job	Run time
quick-build (latest, ubuntu-latest)	3m 23s
quick-build (dev, ubuntu-latest)	3m 18s
quick-build (supported, ubuntu-latest)	3m 33s
opam-build (supported, ubuntu-latest)	4m 44s
opam-build (latest, ubuntu-latest)	4m 42s
nix	2m 19s
build (supported)	3m 38s
opam-build (dev, ubuntu-latest)	4m 11s
build (dev, --warnings)	3m 52s
build (latest)	3m 28s
doc-dep-graphs	4m 4s
doc-alectryon	4m 4s
doc-coqdoc	1m 45s
doc-timing	1m 39s
coqchk (latest)	2m 12s
coqchk (supported)	2m 25s
coqchk (dev)	1m 54s
install (latest)	1m 50s
install (supported)	1m 49s
install (dev)	1m 55s
delete-artifacts	9s
deploy-doc	1s
	1h 0m 55s

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