Simplified ruby interop test files

grpc.gemspec

src/ruby/bin/grpc_ruby_interop_client

src/ruby/bin/grpc_ruby_interop_server

src/ruby/bin/interop/interop_client.rb

src/ruby/bin/interop/interop_server.rb

src/ruby/pb/test/client.rb

templates/grpc.gemspec.template

tools/run_tests/run_interop_tests.py