ticket:10461: Replace use of SharedPtr in MeasureFormat and RelativeDateTimeFormatter with ShredNumberFormat and SharedPluralRules.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@35112 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10461: Merge r35088 to r35112 from trunk.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@35113 251d0590-4201-4cf1-90de-194747b24ca1