RichText: fix caret position when deleting a selected word

[ellatrix]

Description

Fixes #11964 and adds e2e tests.
Also fixes an issue where CTRL+A wouldn't select all blocks if you first select all text in a rich text field by triple clicking and then pressing CTRL+A.

In #11627 I retained deletion handling for uncollapsed selections (meaning text is selected) because I couldn't figure out the problem fast enough with letting it be handled natively again. It turns out TinyMCE is handling the case where an instance is entirely selected, and the React onKeyDown event is only fired after the TinyMCE event, causing TinyMCE to delete the contents first, and then us thinking the field is empty and merging it with the neighbouring block. The solution is to prevent the TinyMCE behaviour in that case, and handle it ourselves.

@notnownikki I also updated the tests you have added, to check if the space is actually there before retyping.

How has this been tested?

See #11964 and above.

Screenshots

Types of changes

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.

[notnownikki]

Thanks for the test fixes and improvements :)

I've gone through all the steps manually and everything works as expected, 👍 from me!

[notnownikki]

Just an aside: is there already an issue open for the caret placement after undoing deletion?

[ellatrix]

Just an aside: is there already an issue open for the caret placement after undoing deletion?

I'm not sure. Caret position in general is never set after undoing changes. It's an old issue that probably needs a bit of work.

[ellatrix]

Thanks for testing @notnownikki!