Simplify how variants are handled #1820

Job	Run time
clippy	2m 13s
nightly	3m 23s
msrv	1m 36s
docs	3m 10s
rustfmt	16s
basics	1s
test_miri (rune)	3m 32s
build_feature (alloc)	3m 27s
test_miri (rune-core)	42s
no_std (ubuntu-latest, minimal)	1m 9s
test_doc	6m 17s
no_std (macos-latest, minimal)	1m 5s
build_feature (cli)	4m 9s
build_feature (cli,doc)	3m 50s
test_miri (rune-alloc)	6m 11s
build_feature (cli,fmt)	3m 57s
test_lib	2m 53s
test_rune	3m 3s
build_feature (doc)	3m 38s
wasm	1m 8s
build_feature (workspace)	3m 15s
build_feature (languageserver)	3m 44s
build_feature (byte-code)	3m 25s
build_feature (capture-io)	3m 18s
build_feature (emit)	3m 22s
	1h 12m 44s

Provide feedback