[FEATURE] UI changes to "Page" module

This patch covers the following changes

 * Move default column layout to a backend_layout configuration (#39603)
 * Change the db_layout code, to use the default backend_layout (#39603)
 * Make UI changes to the columns rendering (#38013)

The move of default column layout to a backend_layout
is in order to ease the styling.

Change-Id: Idc888f910f5e6b86d86d15ee0cb8acd5417e9bb9
Fixes: #38013
Fixes: #39603
Releases: 6.0
Reviewed-on: http://review.typo3.org/13510
Reviewed-by: Stefan Neufeind
Tested-by: Philipp Gampe
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert