feat: Print validation results even when --errors flag is passed

[bitswamp]

Summary

My team wants to integrate the Prism proxy into our CI pipeline, without having to modify all our existing e2e tests to print out the validation errors in case of failure.

This PR changes the behaviour of the --errors flag so that in addition to returning validation errors in the response body (the existing behaviour), the validation failures are also printed in the prism proxy output (similar to the current behaviour without the --errors flag).

Checklist

• The basics
  • I tested these changes manually in my local or dev environment
• Tests
  • Added or updated
  • N/A (I'm open to adding a test, but the change didn't affect any existing tests)
• Event Tracking
  • I added event tracking and followed the event tracking guidelines
  • N/A
• Error Reporting
  • I reported errors and followed the error reporting guidelines
  • N/A

Screenshots

Proxy output with --errors before change:

Proxy output with --errors after change:

[bitswamp]

This PR previously couldn't be merged because the markdown-link-check job didn't run -- I don't know why. I amended my commit with a small markdown change and rebased it onto current master.