Fix crash wher returning from power save on hardware that disconnects connectors when power saving

Main commit:

renderer/native: Don't queue mode set on hotplug power-save on

We need to trigger a mode set on power-save on changes if it's purely about power saving, but when they arrive as part of a hotplug event, we'll handle all that later, in the monitors-changed handling, that contains the new configuration.

This avoids a crash that happens due to the mode set being queued on now disabled connectors.

Closes: #2985 (closed)