rename PsAbstractType to PsType

src/pystencils/backend/arrays.py

src/pystencils/backend/ast/expressions.py

src/pystencils/backend/jit/cpu_extension_module.py

src/pystencils/backend/kernelcreation/context.py

src/pystencils/backend/kernelcreation/typification.py

src/pystencils/backend/symbols.py

src/pystencils/defaults.py

src/pystencils/field.py

src/pystencils/runhelper/db.py

src/pystencils/sympyextensions/typed_sympy.py

src/pystencils/types/__init__.py

src/pystencils/types/basic_types.py

src/pystencils/types/parsing.py

src/pystencils/types/quick.py