Enable strict for mypy

[altendky]

Draft for:

• Changelog entry
• Address remaining issues
• Merge fixes from granular PRs for clearer changes and changelog entries
  • Fill generic parameter as sip.array[int] for QtDataVisualization textures #100
  • Remove unneeded ignores on QIODevice.OpenMode #101
  • fix pyqtSlot result parameter type and Callable generic #102
  • pyqtBoundSignal.disconnect()'s slot parameter is optional #103
  • sip.voidptr handles integer values and sequences #104

[altendky]

PyQt5-stubs/sip.pyi:82: error: Missing type parameters for generic type "array"

https://github.com/altendky/PyQt5-stubs/blob/a42d41d2400d845db0557ad3f621fde42ce5dd30/PyQt5-stubs/sip.pyi#L82

# The voidptr type.
class voidptr:
    <snip>
    def asarray(self, size: int = -1) -> array: ...

---

PyQt5-stubs/QtCore.pyi:9235: error: Missing type parameters for generic type "typing.Callable"

https://github.com/altendky/PyQt5-stubs/blob/a42d41d2400d845db0557ad3f621fde42ce5dd30/PyQt5-stubs/QtCore.pyi#L9235

FuncT = typing.TypeVar('FuncT', bound=typing.Callable)  # For a correct pyqtSlot annotation

https://github.com/altendky/PyQt5-stubs/blob/a42d41d2400d845db0557ad3f621fde42ce5dd30/PyQt5-stubs/QtCore.pyi#L9267

def pyqtSlot(*types: typing.Any, name: typing.Optional[str] = ..., result: typing.Optional[str] = ...) -> typing.Callable[[FuncT], FuncT]: ...