Tests: Block Editor: Register Settings Sidebar

[n7studios]

Summary

Added tests for #1040 for Forms on WordPress Pages

Testing

• PageFormBlockEditorCest: Test that the Plugin settings sidebar in the block editor works, and switching between the block editor and Classic Editor retains settings
• PageFormCest: Updated tests to use the Classic Editor (non-block editor)

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)