Fix: Pages are not being scanned by Language Processing

[dinhtungdu]

Description of the Change

• Add page to rest route check (is_rest_route).
• Add a filter (classifai_rest_bases) to support custom post type with custom rest base.
• Remove unused enqueue.
• Remove deprecated (and removed) function (is_gutenberg_page).

Benefits

Pages now are scanned and tagged by Language Processing.

Verification Process

1. Edit a page then hit the Update button.
2. See the page updated normally without any error.
3. Go back to the pages list, see the page processed by Waston.

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

Closes #161

[ryanwelcher]

@dinhtungdu great work on this! I'm thinking we should have some unit tests to cover pages - any objections?

[ryanwelcher]

@dinhtungdu I'm not sure what we're testing here. I think we want to be sure that when a page is saved, it is being scanned.

[dinhtungdu]

@ryanwelcher I added test for is_rest_route only because it gets updated in this PR and it's the cause of the issue.

The issue only happens for block editor only, so I think WPAcceptance tests will be better fit and more straight forward. We can wait for #179 to be merged then continue work on this?

[ryanwelcher]

@dinhtungdu that works for me - merge away!