PAM wrapper creates /tmp/pam.X files during its execution (strictly as
it does not follow $TMPDIR either), however given the low number of
combinations, we may end up in re-using the same pam.* folder during
meson test, causing a failure.
As per this, remove these temporary files on tearDown so that we won't
try reusing the same folder multiple times.
Fprintd is dependent on the deprecated dbus-glib, also this doesn't provide
various features we can take advantage of, like the ones for async
authentication mechanism.
So, remove all the dbus-glib dependencies and simplify the code, but without
any further refactor, and keeping everything as it used to work, while this
will give room for further improvements in subsequent commits.
Internally, we just use dbus-codegen to generate the skeletons, and we
use the generated FprintdDBusManager with composition, while we
implement the device skeleton interface in FprintDevice, so that we
don't have to use it as a proxy, and keep being closer to what it used
to be with dbus-glib.
Fixes: #61
