Clean Orange.__init__.py

`Orange.__init__.py` has some stuff that is Qt / openGL specific and handles some strange cases. This code unnecessary complicated installation for users that just want to use Orange for scripting (see #5688).

We need to:
- [ ] Figure out what is still necessary. Hopefully, nothing is.
- [ ] Move that necessary stuff somewhere else, perhaps to `Orange.canvas` or to the orange-canvas-core.

This is a `meal` because it required extensive testing.

Start by reading Orange.__init__.py and tracing the Qt/OpenGL-specific cases, then compare what belongs in Orange.canvas or orange-canvas-core. Test installation and scripting-only imports, along with the canvas path; done means unnecessary GUI dependencies no longer complicate scripting while required canvas behavior still works.

Written by the indexing model from the issue text.