Align items in the center within each table row within suggestions.

When differently-sized widgets OR widgets of same size but not filling
space in previews are shown side by side, the top alignment looks odd.

Besides, in the updated UX, we want them to be center aligned.

Bug: 318410881
Bug: 319152349
Flag: N/A
Test: Screenshot update in cl chain.
Change-Id: I52cd7d6a1b5397a3c4c9dea8b072792b3211a8d3