bindep: SUSE & dpkg-based platforms require some fixes

tl;dr:

- On OpenSUSE Tumbleweed, pg_config is provided by postgresql-server-devel
- On OpenSUSE Tumbleweed, qemu-img is provided by qemu-tools (not qemu-img)

Details:

On Tumbleweed, I ran the following commands:

$ tox -ebindep
...
Missing packages:
    gcc libffi48-devel libmysqlclient-devel mariadb postgresql postgresql-devel postgresql-server python3-devel qemu-img
...

$ sudo zypper install gcc libffi48-devel libmysqlclient-devel mariadb postgresql postgresql-devel postgresql-server python3-devel qemu-img

$ tox -epy3
...
Collecting psycopg2>=2.8.4 Using cached psycopg2-2.9.3.tar.gz (380 kB) Preparing metadata (setup.py): started
  Preparing metadata (setup.py): finished with status 'error'
  error: subprocess-exited-with-error × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [25 lines of output]
      running egg_info
      creating /tmp/pip-pip-egg-info-rk_ofq01/psycopg2.egg-info
      writing /tmp/pip-pip-egg-info-rk_ofq01/psycopg2.egg-info/PKG-INFO
      writing dependency_links to /tmp/pip-pip-egg-info-rk_ofq01/psycopg2.egg-info/dependency_links.txt
      writing top-level names to /tmp/pip-pip-egg-info-rk_ofq01/psycopg2.egg-info/top_level.txt
      writing manifest file '/tmp/pip-pip-egg-info-rk_ofq01/psycopg2.egg-info/SOURCES.txt'
      /home/vagrant/glance/.tox/py3/lib/python3.8/site-packages/setuptools/config/setupcfg.py:458: DeprecationWarning: The license_file parameter is dep
recated, use license_files instead.
        warnings.warn(msg, warning_class)

      Error: pg_config executable not found.
...

$ sudo zypper install postgresql-server-devel

# Now pg_config is available

$ which qemu-img
which: no qemu-img in (/home/vagrant/glance/.tox/py3/bin:/home/vagrant/bin:/usr/local/bin:/usr/bin:/bin)

# Installing qemu-tools made qemu-img available.

I still could not run "tox -epy3" successfully because of issues with stestr on this OS, but it's pretty clear that bindep.txt should be fixed for OpenSUSE.