Add accessibility infos to many widgets.

This MR adds accessibility infos to many widgets to make it easier to navigate.

When working on the tooling for creating tutorial videos I expereinced that it's quite complicated to find the correct part/region of the GUI. While not being an accessibility expert I assume this not only effects my tooling, but much more important people depending on accessibility. This s especially true since the accessibility tree contains a lot of unnamed and unlabled items.

I'd appreciate if this patch would be backported to older 6.x versions. (Please let me know whether I can backport and how.)