try fix for offscreen rendering on Windows
The context was getting cleaned too often maybe. This fix reverts one line from commit https://gitlab.kitware.com/vtk/vtk/commit/ 3a8e4497 This commit fixes issue vtk/vtk#16876 and adds a test for that condition as well as a few other cases that should work but could cause problems. This change could introduce other issues limited to windows as the code is fairly complex and the use cases vary widely. At some point the whole process of creating windows and handling offscreen drawing needs to be reworked. It is a mishmash of 20 years of code and overdue for a real workover for all platforms. But this topic is intended to fix this one case until we have time to really look at it and rework it. Currently the new test is only active for OpenGL2 and Windows. OpenGL1 and other platforms has issues with it that need to be fixed in the future. But for now this change fixes the reported Windows issues and adds a test to maintain that fix.
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