Up java.text.DecimalFormat max integer digits.

Android M and before used native ICU4C NumberFormat for
java.text.DecimalFormat and that had a max integer digits of 2000000000.
To maintain compatibility with earlier Android releases, use that value
for java.text.DecimalFormat.

The underlying android.icu.DecimalFormat is modified to allow maximum
integer digits bigger than 309 (but keeping the default values
unchanged).

Also add test for DecimalFormat with pattern "00" (fixed by related
revert in external/icu)

Bug: 27855939
Change-Id: I8d83e3392d7f87cdfbda8c6fbc40a775809ab4c1