Implement a K/V parser library
The key/value format K=V is used extensively in the Tor code and seems many places uses their own way to parse that.
This ticket is for implementing a library to parse such K/V construction. There is a world where we might require V to be quoted or not so I'll let this challenge to the implementer(s).
This ticket comes from the work done in #28179 (moved) that implements messages from the PT to the Tor process.