Introduces test infrastructure and mockup classes for
`dbus_middleware1`. Includes `BusProvider` test setup, fake device
implementations, and initialization logic to support session bus
testing. Enhances testability and isolation of the D-Bus middleware
components.
For local and automated testing of the source code, the testing
folder is added. This includes all the tests that the module has to
go through. The project also uses pytest-cov, which can also create
coverage reports.
