Update `_AuxPanel.pcss` (#10888)
* Fix class names - from m_ to mx_
* Move mx_RoomView_auxPanel from _RoomView.pcss to _AuxPanel.pcss
The class name 'mx_RoomView_auxPanel' belongs to AuxPanel, not RoomView
* Correct naming
* Strictify: mx_RoomView_auxPanel *
* Nest mx_AuxPanel_stateViews_span
* Sort
* Run prettier
* Use custom properties
* Revert "Use custom properties"
This reverts commit fe720d05f4572e74e71887203d43c491f0723a92.
