feat: add crop command

[dinhtungdu]

Description of the Change

This PR add new crop command to "smart crop" uploaded images. This command output detailed error about the whole process which help trouble shooting easier and more straight forward.

Some example of errors outputed:

Fetching images ...
Fetching images ... DONE (1)
Cropping 1 images ...  100% [==================================================] 0:02 / 0:02
1842:150x150: The value '1' is not valid. (classifai_smart_cropping_api_validation_errors).
Error: Cropped 0 images, 1 errors.

Fetching images ...
Fetching images ... DONE (1)
Cropping 1 images ...  100% [==================================================] 0:01 / 0:02
1842:150x150: Image URL is not accessible. (InvalidImageUrl).
Error: Cropped 0 images, 1 errors.

$ wp classifai crop
Error: Smart Cropping is disabled. Enable it in Image settings to use this command.

Verification Process

Please test this PR on a live server without CND plugin enabled.

1. Disable Smart Cropping.
2. Upload an image.
3. See the thumbnail is not "smart cropped".
4. Run wp classifai crop.
5. See error "Smart Cropping is disabled.".
6. Enable Smart Cropping.
7. Run wp classifai crop again
8. Due to the API error which is addressing in Fix: Smart cropping results not as expected #229, you will get api validation error. Apply the fix on that PR, you will see the thumbnail get cropped correctly.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

Fixes #176

Changelog Entry