AesInvalidKeySize skip 192 on SB devices

This change clarifies the language to specify that StrongBox devices
must only support key sizes of 128 and 256. Additionally, it changes the
new AesInvalidKeySize test to only enforce against StrongBox instances
on devices that launch on S or later, not previously launched devices.

Ignore-AOSP-First: CP to AOSP
Bug: 191736606
Test: Test passes on a StrongBox enabled device
Change-Id: Ic0ff19d2d19d6e18dfbc0fad4b8182264f36b2f6