[automerger skipped] DO NOT MERGE Cherry-pick: ICU-20536 Japanese era Reiwa support in ICU4J 58 am: fc5a01ba3d -s ours am: 8eb668d374 -s ours
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am skip reason: subject contains skip directive

Change-Id: I36b54533ebd60cfa8fdd7d2a52bb7a1a32da91dd