Rust: add tests for protover edge cases

There are more tests for legacy/trac#27164 (moved) and legacy/trac#27177 (moved) in branch prototest1 on ​https://gitgud.io/onionk/tor.git

Since we backported the fixes, I suggest we backport the tests.

Original comment: https://trac.torproject.org/projects/tor/ticket/27164#comment:7