Add OCaml 5.1 to CI #755

Job	Run time
core (ubuntu-latest, 4.08, true, true, *.opam )	6m 43s
core (ubuntu-latest, 4.08, false, true, *.opam )	5m 54s
core (ubuntu-latest, 4.09, true, true, *.opam )	6m 47s
core (ubuntu-latest, 4.09, false, true, *.opam )	6m 10s
core (ubuntu-latest, 4.10, true, true, *.opam )	6m 48s
core (ubuntu-latest, 4.10, false, true, *.opam )	6m 26s
core (ubuntu-latest, 4.11, true, true, *.opam )	6m 38s
core (ubuntu-latest, 4.11, false, true, *.opam )	6m 0s
core (ubuntu-latest, 4.12, true, true, *.opam )	6m 22s
core (ubuntu-latest, 4.12, false, true, *.opam )	5m 43s
core (ubuntu-latest, 4.13, true, true, *.opam )	6m 44s
core (ubuntu-latest, 4.13, false, true, *.opam )	5m 44s
core (ubuntu-latest, 4.14, true, true, *.opam )	6m 7s
core (ubuntu-latest, 4.14, false, true, *.opam )	5m 27s
core (ubuntu-latest, 5.0, true, true, *.opam )	6m 29s
core (ubuntu-latest, 5.0, false, true, *.opam )	5m 42s
core (ubuntu-latest, 5.1, true, true, *.opam )	3m 9s
core (ubuntu-latest, 5.1, false, true, *.opam )	5m 34s
core (ubuntu-latest, ocaml-variants.5.1.1+options,ocaml-option-flambda,ocaml-option-musl,ocaml-op...	1m 14s
core (macos-latest, 4.14.x, true, true, *.opam )	14m 40s
core (windows-latest, 4.14.x, false, true, *.opam )	6m 32s
core (ubuntu-latest, 4.08.x, true, false, *.opam !lwt_ppx.opam )	5m 37s
core (macos-latest, 4.08.x, true, false, *.opam !lwt_ppx.opam )	8m 37s
core (windows-latest, 4.08.x, false, false, *.opam !lwt_ppx.opam )	4m 3s
	2h 29m 10s

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