Cleanup `PyBuffer` a bit by lostmsu · Pull Request #1662 · pythonnet/pythonnet

@lostmsu

@lostmsu

- better finalizer, that actually calls PyBuffer_Release
- improved input parameter handling for common routines
- added support for copying data to/from large Python buffers

fixes pythonnet#1556

filmor

approved these changes Jan 6, 2022