[TASK] Bring Toolbar styling for Bootstrap HTML5 markup

Toolbar now is based on Bootstrap compatible HTML5 markup.
Styles all elements. Removes the previous CSS compatibility layer.

Layout in Toolbar dropdown menu is out of scope (#62927, …).

Resolves: #62939
Releases: master
Change-Id: I701fd7862db331a54fc1f8514c3839e9c8e1be9d
Reviewed-on: http://review.typo3.org/34141
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>