Allow packaging salt-ssh as a package.

This works by passing `--ssh-packaging` to the `sdist` command

```
python setup.py sdist --ssh-packaging
```
Also include `salt-run` in the packaged scripts
Add `salt-call` to the available scripts and allow packaging with setuptools
Merge pull request #16298 from s0undt3ch/features/ssh-packaging

Allow packaging salt-ssh as a package.