[RUBY] Stop using deprecated `URI.encode`

[kitop]

Description

Ruby's URI.encode has been deprecated over 10 years ago. In addition, Ruby 2.7 now shows the warning in non-verbose mode, resulting in very noisy logs.

Swagger-codegen version

2.4.15, and previous

Swagger declaration file content or url

N/A

Command line used for generation

./run-in-docker.sh /gen/bin/ruby-petstore.sh

Steps to reproduce

Generate the Ruby code, see URI.escape used in api_client.rb and configuration.rb files

Related issues/PRs

Couldn't find.

Suggest a fix/enhancement

URI.encode is a very simplistic percent-encoding replacement. This is not always correct, as it may vary on differenet parts of the URI.
We could copy the code from URI.escape to a Utils module, or inline it in each class, but we would still be doing a non-optimal encoding.
Another solution is to add a dependency on the addressable gem, and use Addressable::URI.encode which is part-aware. It adds one small dependency, but the escaping would be much better. That gem is also used by a lot of other gems, so might not be a big impact in the end user application.

[kitop]

Closed via #10445