[backport] vtkPythonInterpreter: release GIL in SetupPythonPaths

Client applications that initialize Python prior to initializing vtkPythonInterpreter and which add Python search paths would hang because the GIL was not released on Windows with Python version > 3.8 after DLL search paths were added. Fixed that by using the default vtkPythonScopeGilEnsurer constructor, which defaults to releasing the GIL.

(cherry picked from commit 25b17126)

Backport: paraview/release