[zero-copy] Re-add no_std support, add separated_by_exactly, and a few primitives

[wackbyte]

Adds the any, empty, one_of primitives, the separated_by_exactly combinator, and no_std support back.

[zesterer]

Thanks!

[wackbyte]

for posterity, here are the benchmarks after using the new separated_by:

compared to previously, where a combo of other combinators was used in place of it: