[automerger skipped] DO NOT MERGE Cherry-pick: ICU-20536 Japanese era Reiwa support in ICU4J 56 am: 18c03b9631 -s ours am: b0ffb16c65 -s ours am: 0787e23688 -s ours am: b67a881144 -s ours am: 1e7cf5bdda -s ours am: 91a1624233 -s ours
am: 4258d66d4e

Change-Id: If9e7af3d1d439f5f75d6d50d3ae28d47b2423067