unstarted_runtime: Update references to decimal format classes.

We had a few special cases for thread local buffers and instances
created by our formatters / parsers. Update them to point to the
OpenJdk equivalents of the same classes.

bug: 27265238

(cherry picked from commit a1e93127)

Change-Id: I56b0a4dd19762665393a205c1f6f0e549451f0f4