[Ruby] Add support for Faraday (HTTP lib) #3270

Description

Currently, Ruby API client has a dependency on Typhoeus (HTTP lib).

We want to add support for Faraday to provide more flexibility in choosing what HTTP lib to use in the Ruby API client.

(Typhoeus will still be supported)

OpenAPI Generator version

Latest master

Suggest a solution

Similar to Java, we can use the -l/--library option to specify faraday and implement the api_client.rb with faraday so that users can choose which one they want to use.

cc @meganemura