Rework section for dietpi-drive_manager

[Joulinar]

Section for dietpi-drive_manager would need to be updated due to

• DietPi-Drive_Manager | Add USB auto-mount hotplug feature DietPi#8058
• dietpi-drive_manager: Update fstab entries individually instead of rewriting from scratch DietPi#8056

[MichaIng]

For completeness, this has some impact as well: MichaIng/DietPi@af46989
It caused a regression addressed here (along with another older regression): MichaIng/DietPi@acbb506
But there seems to be something else not behaving as expected, which I want to understand before pushing a live patch.

[MichaIng]

Done: MichaIng/DietPi#8099