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.
Built from https://develop.svn.wordpress.org/trunk@30318


git-svn-id: http://core.svn.wordpress.org/trunk@30317 1a063a9b-81f0-0310-95a4-ce76da25c4cd