Remove debian packaging rules

[antoninbas]

This is a proposal to remove https://github.com/p4lang/ptf/tree/main/debian
There is no one to maintain it and it has not been updated for 7 years. As it stands today, it is probably not useful to anyone.

Note that we now distribute PTF has a PyPI package, with the package being automatically updated when a new Git tag is created.

I plan to leave this issue open for a couple of weeks. After that delay, if no one has complained (or volunteered to maintain the python-ptf debian package for some current distributions), we will just remove the debian/ folder.