fix: re-enable foldhash by default, but exclude it from zkvm (#777) #2097

Job	Run time
miri --no-default-features	4m 54s
miri	5m 4s
test ubuntu-latest stable --no-default-features	1m 22s
miri --all-features	7m 3s
test ubuntu-latest stable	1m 58s
check no_std	51s
test ubuntu-latest nightly --no-default-features	2m 49s
test ubuntu-latest nightly	1m 45s
clippy	2m 45s
docs	54s
test ubuntu-latest 1.79 --no-default-features	37s
test ubuntu-latest 1.79	44s
test windows-latest stable --no-default-features	3m 48s
features stable	2m 22s
test windows-latest stable	2m 49s
wasm	42s
features stable --all-targets	3m 21s
test windows-latest nightly --no-default-features	3m 5s
features nightly	2m 43s
test windows-latest nightly	3m 5s
features nightly --all-targets	3m 43s
test windows-latest 1.79 --no-default-features	1m 46s
test windows-latest 1.79	1m 49s
test ubuntu-latest 1.79 --features json	2m 18s
test windows-latest 1.79 --features json	2m 0s
fmt	1m 52s
test ubuntu-latest nightly --all-features	1m 29s
test windows-latest nightly --all-features	3m 26s
	1h 11m 4s

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