Move HighlightChip interface to ShadeHighlightChip

ShadeHighlightChip was moved to a separate file in ag/34791265. We
should move the HighlightChip interface out of ShadeHeader as well as a
result.

Bug: None
Flag: EXEMPT clean up
Test: ShadeHeaderViewModelTest
Change-Id: I448eaedc00dd50a05303c2778ef222ef732ad6e2