ticket:10461: Add test for LRUCache and SharedPtr.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@34567 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10461: Preliminary proof of concept. Cache DecimalFormatSymbols only within DecimalFormat. Resulted in a 3X increase in creation of DecimalFormat. 44us down to 14.3us when creating from scratch; 3.4us down to 1.02us when cloning

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@34568 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10461: Proof of concept phase 2. Add NumberingSystemCache. DecimalFormat creation down from 44us to 7.7us. DecimalFormat cloning down from 3.4us to 1.05us. This phase does not affect cloning as NumberingSystem objects are used as temporary objects when creating DecimalFormat objects.

git-svn-id: http://source.icu-project.org/repos/icu/icu/branches/tkeep@34570 251d0590-4201-4cf1-90de-194747b24ca1