Fixing too wide hover state in shade header

The problem is: shade_header_system_icons will be forced by constraints to stretch from date view to right edge of shade. Without start constraint it will overlap with date when font is big enough.
What I've tried:
- modifying qs_header constraints so that it will be wrap_content but still respect "start" constraint using various flavours of "layout_constraintWidth_default", "layout_constraintWidth", "layout_constraintWidth_max", "layout_constrainedWidth" and different widths: either 0dp or wrap_content
- using constraint chain "spread_inside" attribute - it didn't respect "start" constraint
- adding Space between date and system icons - this forces system icons to be too small

None of above worked so I resorted to adding container inside shade_header_system_icons that will be just to represent hover bounds and will be right aligned inside stretched parent.

Fixes: 295138618
Test: hover over system_icons in expanded QS state and see hover bounds are correct
Test: change font size and display size to the biggest possible values and see system icons doesn't overlap with date
Change-Id: I892c645d1c01d9491321c833fb17c563e1291254