Ensure we save the modified title and use that when we insert a title

[dkotter]

Description of the Change

As described in #508, any edits made to generated titles before they are inserted don't persist. The problem lies in how we save edited titles and which title we use when inserting. Basically we weren't saving the edited title to state and we were using the raw generated title when inserting.

This PR changes both to ensure any edits made persist to our state object and then we use the state object when a title is inserted.

Closes #508

How to test the Change

1. Ensure the Title Generation feature is on
2. Generate titles for a piece of content
3. Choose one of those titles, don't make any edits and then select it
4. Ensure the title of your content updates correctly
5. Generate titles again and this time edit one of the titles
6. Select to use the edited title and ensure the title of your content updates correctly with those edits

Changelog Entry

Fixed - Ensure any edits made to generated titles persist when inserting said title

Credits

Props @dkotter

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[dkotter]

Reviewer note: removing this from our test matrix for now as it's causing tests to fail due to 10up/cypress-wp-utils#98

[Sidsector9]

Tested and works well 👍