Fix PerMill sign in DecimalFormatSymbols - part 2

- Percent and permill sign should be treated the same.
  Store full-length permill sign string in LocaleData,
  and truncate in DecimalFormatSymbols

Bug: 67034519
Bug: 67862550
Test: cts-tradefed run cts -m CtsLibcoreTestCases --test
libcore.java.text.DecimalFormatTest
Test: vogar libcore.java.text.DecimalFormatTest
Change-Id: I4c8f43326e359f74703fe35e5481775de553b053