Add UX string tweaks before string freeze.

We're fully intending to implement some string and layout tweaks
requested by UX, but we need to get the requested strings checked
in before the strings deadline.  We carefully keep existing (legacy)
strings intact to avoid any runtime crashes until we get the layout
work done.

Test: builds, boots
Bug: 76097999
Change-Id: Ic6531de170df8eaa8b3a0a23d76a0c8821bb5b16