One Layout per QPlainTextEdit

For Qt Creator we have multiple issues with the current layout.

With one layout per document instead of widget we are not able to use word wrap in both widgets at the same time (see the minimal example in main.cpp). It will always wrap the document for the bigger widget and the smaller widget will get a scrollbar, which is kind of unexpected.

Another issue is that blocks can not be set visible in individual widgets. Resulting in not being able to fold a block in one widget but keep it expanded in another one.

We also would like to show additional content in individual widgets, for that we are expanding the blockBounding rect for blocks. but this results in having the increased bounding rect in all widgets, while we need the additional space in just a single one.