[REQ][Ruby] Add support for faraday 2.x

[ykitamura-mdsol]

Is your feature request related to a problem? Please describe.

Faraday 2.x is released: lostisland/faraday#1358

Describe the solution you'd like

Based on the UPGRADING guide, we need to make changes to the following files:

gemspec.mustache

Relax Faraday dependency and add s.add_runtime_dependency 'faraday-multipart'

openapi-generator/modules/openapi-generator/src/main/resources/ruby-client/gemspec.mustache

Lines 22 to 24 in 510f799

	{{#isFaraday}}
	s.add_runtime_dependency 'faraday', '~> 1.0', '>= 1.0.1'
	{{/isFaraday}}

api_client.mustache

Add require 'faraday/multipart' if Gem::Version.new(Faraday::VERSION) >= Gem::Version.new('2.0')

openapi-generator/modules/openapi-generator/src/main/resources/ruby-client/api_client.mustache

Lines 13 to 15 in 510f799

	{{#isFaraday}}
	require 'faraday'
	{{/isFaraday}}

api_client_faraday_partial.mustache

Handle basic_auth like this to support both Faraday 1.x and 2.x.

openapi-generator/modules/openapi-generator/src/main/resources/ruby-client/api_client_faraday_partial.mustache

Line 16 in 510f799

conn.request(:basic_auth, config.username, config.password)

I'm going to work on this if no one has already started.