[automerger skipped] DO NOT MERGE Cherry-pick: ICU-20536 Japanese era Reiwa support in ICU4J 58 am: fc5a01ba3d -s ours am: f04b16ccf8 am: e5e23d04ec am: a837b28d8f -s ours
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Change-Id: I7437ff0be93c13db6c8da780977c7058fe3fb231