Special-case English for DateTime and Time key listeners

Because English time patterns use uppercase letters by default (and a
comma to separate date and time when both are represented), we were
concluding they need internationalized input. Although they
literally do, let's keep the world simple and assume they don't need
internationalized input.

Compared to Nougat, we will now accept uppercase AM and PM and comma
for English if the IME allows them, we just continue to not signal
that an internationalized layout is needed.

Test: CTS tests pass
Bug: https://code.google.com/p/android/issues/detail?id=2626
Bug: https://code.google.com/p/android/issues/detail?id=82993
Bug: 8319249
Bug: 33276673
Bug: 34394455
Bug: 37079150
Change-Id: I82bfde323ba49ae1a27ff5c2e729063b7d81dcc8