Simplify how variants are handled #1822

Job	Run time
clippy	2m 9s
nightly	3m 28s
msrv	1m 37s
docs	2m 58s
rustfmt	21s
basics	1s
wasm	1m 9s
no_std (ubuntu-latest, minimal)	1m 10s
no_std (macos-latest, minimal)	1m 9s
test_doc	6m 18s
build_feature (alloc)	3m 26s
build_feature (cli)	4m 10s
build_feature (cli,doc)	4m 4s
test_miri (rune)	3m 18s
test_lib	2m 59s
build_feature (cli,fmt)	4m 4s
test_miri (rune-core)	44s
test_rune	2m 42s
build_feature (doc)	3m 46s
test_miri (rune-alloc)	6m 7s
build_feature (workspace)	3m 34s
build_feature (languageserver)	4m 2s
build_feature (byte-code)	3m 22s
build_feature (capture-io)	3m 27s
build_feature (emit)	3m 22s
	1h 13m 27s

Provide feedback