change to generic energy report filenames for consistent redirect links

In order to have a redirect link that remains usable for new energy consumption reports, I have renamed the standard usage scenario and idle mode reports to have a more generic name, namely:

• 2022-09-22_Okular_energy-consumption_SUS_de.pdf => okular_energy-consumption-report_SUS.pdf
• 2022-09-22_Okular_energy-consumption_Idle_de.pdf => okular_energy-consumption-report_idle.pdf

Regarding redirect links, see discussion at: frameworks/kcoreaddons!374