fix(non linear font scaling): date textview might be covered by system icons in qs header

As b/291168601, when the sum of date textview width and system icons container width is larger than the qs header width, date textview would be covered by system icons. Therefore, in xml/qs_header we add the constraint between the date textview and the system icons to prevent the ui broken.

Bug: 291168601
Test: manually - attached screenshots in bug
      atest CombinedShadeHeaderConstraintsTest
Change-Id: Ifd13da3bd3e7893bc79b0114fce972b039261364