batch renderer destructor

[nim65s]

panda3d batch renderer needs to be deleted to stop its subprocesses:

happypose/happypose/toolbox/renderer/panda3d_batch_renderer.py

Line 347 in 6f06ad7

def __del__(self) -> None:

but its destructor might not be called, and the scripts might hang forever, eg in cosypose run_inference_on_example, where the scope is never destroyed.

This can be quickly workaround by creating main() functions, but it should be refactored to avoid this kind of issues.