Remove code that adds Classic Editor links

[dkotter]

Description of the Change

As discussed in #22, the ideal for this plugin is to focus on converting content from the Classic Editor to the new Block Editor. While it's nice to provide a way for users to still edit content in the Classic Editor, it can be argued that is out of scope for this plugin and is better off handled by other plugins (like the official Classic Editor plugin). This also prevents conflicts with plugins like those.

This PR attempts to remove any code that adds Classic Editor links. This includes:

• Link in the Admin Menu Bar when editing an item, that allows you to switch between the Classic and Block editor
• Link in the Admin Menu Bar when viewing an item on the front-end, that allows you to edit that item in the Classic editor
• Link in the sidebar menu for supported post types, allowing the creation of new items in the Classic Editor
• Link above the post list table for supported post types, allowing the creation of new items in the Classic Editor
• Link that shows inline within the post list table, allowing you to edit that item in the Classic Editor

Alternate Designs

Instead of removing this functionality, there are two other options that were discussed:

1. Keep this functionality in place, not caring that it conflicts with the official Classic Editor plugin
2. Keep this functionality in place but only load it if the Classic Editor plugin isn't being used

The second approach there I think is the most intriguing but the overall out-of-scope argument still applies. If a user wants to still edit content in the Classic Editor, they are probably better off using the official Classic Editor plugin.

Benefits

We remove code that doesn't directly solve the problem this plugin is attempting to solve, namely converting content from the Classic Editor to the Block Editor. Also avoids any conflicts for users that will be running both this plugin and the official Classic Editor plugin.

Possible Drawbacks

We are removing functionality that has already been built, which always leaves a slightly bad taste in my mouth

Verification Process

Install the plugin with these changes and ensure any link that goes to the Classic Editor no longer exists. Then install the official Classic Editor plugin and ensure no duplicate Classic Editor links are shown but the Classic Editor links that are now in place still work.

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

#22

[jeffpaul]

@dsawardekar @tlovett1 either of you care to review this as the last remaining item before we'd be ready to start the 1.0.1 release process?

[dsawardekar]

Thanks @dkotter I tested this locally, and it works as described in the task. 👍

@jeffpaul I would suggested tagging the current version before merging in case we need to use the old implementation.

[dinhtungdu]

Tested and this PR worked great on my end.