[automerger skipped] DO NOT MERGE Cherry-pick: ICU-20536 Japanese era Reiwa support in ICU4J 58 am: fc5a01ba3d -s ours am: 8eb668d374 -s ours am: 3f055f5bde -s ours am: 43be8bba2a -s ours am: 29967cf6f2
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Change-Id: I51548f46400ac3b1a9c329b8a01d63df01aafb37