Optimize compilation of switch statements for untagged variants #5209

Job	Run time
build-rewatch (macos-13, x86_64-apple-darwin)	23s
build-compiler (ubuntu-latest, ocaml-variants.5.2.0+options,ocaml-option-static, true, true, true...	2m 45s
build-rewatch (macos-14, aarch64-apple-darwin)	13s
build-compiler (buildjet-2vcpu-ubuntu-2204-arm, ocaml-variants.5.2.0+options,ocaml-option-static,...	3m 12s
build-rewatch (ubuntu-latest, x86_64-unknown-linux-musl)	6s
build-compiler (macos-13, 5.2.0, true)	4m 34s
build-rewatch (buildjet-2vcpu-ubuntu-2204-arm, aarch64-unknown-linux-musl)	16s
build-compiler (macos-14, 5.2.0, true)	2m 17s
build-rewatch (windows-latest, x86_64-pc-windows-gnu)	19s
build-compiler (windows-latest, 5.2.0, true)	3m 18s
build-compiler (ubuntu-latest, ocaml-variants.5.0.0+options,ocaml-option-static)	1m 54s
build-compiler (ubuntu-latest, ocaml-variants.4.14.2+options,ocaml-option-static)	1m 36s
build-compiler (ubuntu-latest, ocaml-variants.4.13.0+options,ocaml-option-static)	1m 45s
package	25s
installationTest (macos-13)	22s
installationTest (macos-14)	17s
installationTest (ubuntu-latest)	14s
installationTest (buildjet-2vcpu-ubuntu-2204-arm)	46s
installationTest (windows-latest)	42s
publish	0s
	25m 24s

Provide feedback