[FEATURE] Support custom width in TCA tree

Introduce setting ['config']['treeConfig']['appearance']['width']
to apply custom width for TCA select fields that use the tce tree.

Change-Id: I757745e51f650c20f23e60aa6c4a9b7b0fca6b99
Releases: 6.0
Resolves: #39046
Reviewed-on: http://review.typo3.org/12860
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn