Rework tmpdir & associated a bit.

- Split out tmpdir logic into a separate entity & add the appropriate
  arguments and checks.
- sysb can be removed since there is now no associated logic.
- Move disk/etc logic into tmpdir.py.

lib/utils.py

@@ -5,7 +5,7 @@ This file contains a few self-contained helper functions
 
 # SPDX-License-Identifier: GPL-3.0-or-later
 # SPDX-FileCopyrightText: 2021 Andrius Štikonas <andrius@stikonas.eu>
-# SPDX-FileCopyrightText: 2021-22 fosslinux <fosslinux@aussies.space>
+# SPDX-FileCopyrightText: 2021-23 fosslinux <fosslinux@aussies.space>
 
 import os
 import shutil