Changes to validate CLI tokens

[sr010]

Changes to validate CLI tokens

Test case where CLI tokens are invalid: https://github.com/shamantraghav/twilio-cli-core/actions/runs/1822859463

Test case where CLI tokens are valid: https://github.com/shamantraghav/twilio-cli-core/actions/runs/1822868587

Also review: https://github.com/twilio/twilio-cli/pull/389

Checklist

• [x] I acknowledge that all my contributions will be made under the project's license
• [ ] 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 file a support ticket, or create a GitHub Issue in this repository.