Revert "ICU: Drop test/ version of DecimalFormat_ICU58 and friends."

Revert: Decided to apply this change as a local change to icu4j/
as opposed to a change to the code generation.

Bug: 68696705
Test: Treehugger at subsequent CL.

This reverts commit 430456d6e8fd3a9734218d3072cdba932ec669d2.

Change-Id: I732f6aee8d1dcd3532b3f6a286a2af903997e2f7
8 files changed