[TASK] Configurable width of the Element Browser

The width of the element browser is sadly hardcoded to 600 and 650.

In many situations the element browser would need more place and
with this tiny change it would be easily possible to change
that behaviour without overloading the whole file.

Resolves: #58031
Releases: 6.2
Change-Id: I8a7df0e1c8f2c977af309fe5917c38ec6de99759
Reviewed-on: https://review.typo3.org/29555
Reviewed-by: Laurent Cherpit
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer