Bump versions in preparation for 0.2.0 release.

Not all of these strictly need to be bumped to 0.2.0; many could go
to 0.1.1 instead.  But since everything at the tor-rtcompat and
higher layers has had breaking API changes, it seems not so useful
to distinguish.  (It seems unlikely that anybody at this stage is
depending on e.g. tor-protover but not arti-client.)

Unlike the rest of the crates, these don't have a "tor-" or "arti-"
prefix, and are potentially used by code outside arti.  With that in
mind, it's probably for the best not to bump them to 0.2.0 along
with the rest of our crates.

They have had no changes since 0.1.0 other than refactoring and
changing of clippy lints.  Therefore, I'm not bumping the
dependencies from other crates onto these: it's fine whether our
other crates use caret/retry-error 0.1.0 or 0.1.1.