Refactor slice renderer to handle different card width

- Refactor SliceContextualCardRenderer to support for displaying slice
in half/full width card.
- Add two helper classes to separately deal with different card width.

Only the skeleton of the half card helper is put in this CL, the
implementation hasn't been filled in yet. Will implement the detail in
next CL.

Bug: 119655434
Test: visual, robotests
Change-Id: Iacdc90c23bf41cfa7ccae3c0c70a3b663e89307d