Update DietPi-Tools docu area

[StephanStS]

Due to MichaIng/DietPi#7978, some of the entries have changed.

1. Update screenshot of DietPi-Launcher
   1. Changes to be done there: https://dietpi.com/docs/dietpi_tools/
2. Re-order descriptions of the categories due to the changed entry order
3. Add description of DietPi-Benchmark
   1. Changes to be done there: https://dietpi.com/docs/dietpi_tools/#misc-tools

[MichaIng]

Screenshot update still outstanding. PR at main branch has been merged, so it can be done via dev branch.