Testing of toolbx container environment

**Is your feature request related to a problem? Please describe.**
Toolbx is a tool creating containers with specific parts of the host system made available. Currently the availability of said parts is not assured due to no appropriate test suite existing.

**Describe the solution you'd like**
Create a test suite that is generally executable and that is capable of testing the capabilities of toolbxes made out of Toolbx images. These tests could include among others tests for the availability of devices, interaction with host's systemd, DBus (both system and session bus), interaction with `/sys/kernel` and many others.

No files or existing tests are named. Start by reviewing how Toolbx images expose devices, the host systemd and system and session DBus buses, and /sys/kernel; then define a generally executable suite covering those capabilities. Done means the suite runs against Toolbx images and verifies the requested host integrations.

Written by the indexing model from the issue text.