Add semi-additive categories infrastructure #3912

Job	Run time
build (supported)	3m 56s
build (latest)	3m 45s
opam-build (latest, ubuntu-latest)	4m 37s
nix	2m 12s
build (dev, --warnings)	3m 52s
quick-build (supported, ubuntu-latest)	3m 21s
opam-build (supported, ubuntu-latest)	4m 26s
quick-build (dev, ubuntu-latest)	3m 26s
opam-build (dev, ubuntu-latest)	4m 18s
quick-build (latest, ubuntu-latest)	3m 40s
doc-alectryon	1m 26s
doc-dep-graphs	1m 26s
doc-coqdoc	1m 27s
install (supported)	1m 28s
install (dev)	1m 28s
doc-timing	1m 27s
install (latest)	1m 27s
coqchk (latest)	1m 26s
coqchk (dev)	1m 25s
coqchk (supported)	1m 27s
deploy-doc	1s
delete-artifacts	9s
	52m 10s

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