chore: add support for multiple response schemas in php

[tiwarishubham635]

Fixes

Earlier, for operations having different response schemas under the same resource we combined the properties to make a single response schema
Changed the implementation to dynamically generate separate class files for each response schema and return the correct response schema for respective operation

Checklist

• I acknowledge that all my contributions will be made under the project's license
• Run make test-docker
• Verify affected language according to the code change:
  • Generate twilio-java from our OpenAPI specification using the scripts/build_twilio_library.py using python scripts/build_twilio_library.py path/to/twilio-oai/spec/yaml path/to/twilio-java -l java and inspect the diff
  • Run make test in twilio-java
  • Create a pull request in twilio-java
  • Provide a link below to the pull request, this ensures that the generated code has been verified
• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the Contribution Guidelines and my PR follows them
• I have titled the PR appropriately
• I have updated my branch with the main branch
• I have added tests that prove my fix is effective or that my feature works
• I have added the necessary documentation about the functionality in the appropriate .md file
• I have added inline documentation to the code I modified

If you have questions, please create a GitHub Issue in this repository.