Convert `RESPTranslator.ParsingError` from enum to struct
Motivation:
Much like the change for RedisClientError
(6471a2) any error enum that we may want to change will necessitate a major SemVer.
To avoid this, we need to use the established struct-as-enum pattern.
Modifications:
- Change:
RESPTranslator.ParsingError
to be a struct backed by an enum
Result:
The library should be able to evolve to add more RESPTranslator.ParsingError
cases without becoming a breaking change.