Use 'micropackage/requirements' instead of TGMPA

[cliffordp]

Consider using https://github.com/micropackage/requirements instead of TGMPA

Would have to play with it to see how error messages are sent.

https://github.com/afragen/wp-dependency-installer is another alternative.

[cliffordp]

https://github.com/wearerequired/wp-requirements-check exists