TinyMCE: enhance the inline toolbar for images:
- Add alignment (left, center, right, none) buttons.
- Position the menu above the image when possible, except on iOS.
- Fix selecting images on iOS.
First run, part props avryl. See #30147.

git-svn-id: https://develop.svn.wordpress.org/trunk@30318 602fd350-edb4-49c9-b593-d223f7449a82