Wallet card carousel screen UI polish.

1. Adjust header icon size, 50dp -> 56dp, and increase the top margin
2. Update header icon color for locked state
3. Show both "show all" (app button) and "unlock to pay" (action button) in locked screen
4. Update the colors of the buttons

Test: manually test on device
Bug: b/184905963
Change-Id: I53d6cab7fb0adee412d89408481fcf8926e1a29f