[automerger skipped] DO NOT MERGE Cherry-pick: ICU-20536 Japanese era Reiwa support in ICU4J 58 am: fc5a01ba3d -s ours am: f04b16ccf8 am: e5e23d04ec
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Change-Id: I8d47d93d6e587ffc40a67bffbf1ccee205e7c49a