[TASK] Optimize the tree of the form editor

- remove linebreak in root node
  -> instead use text-overflow: ellipsis
- fix indentation of tree elements
  -> move triangles indicating subtrees to the left
- changed tooltip message to only show "id = <element-id>"

Resolves: #85042
Releases: master
Change-Id: I2621974c2688ac5e03a7e39e8c4f6ad94e15e9a4
Reviewed-on: https://review.typo3.org/57007


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Tested-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>