Fix DecimalFormat.format(bigDecimal, sb, new FieldPosition(NumberFormat.Field.CURRENCY))

The variable name was wrong likely since Android 6.0, and thus the field
position is always wrong when formatting BigDecimal or BigInteger > 64-bit.

On Android 11, it's likely that ICU4J DecimalFormat implementation has
been changed, and throws IllegalArgumentException.

Bug: 168304209
Test: atest CtsLibcoreTestCases
Change-Id: I36c6e5ad4d0fd89d0b0a9eb359fe8c060562e227
2 files changed