Switch from jarjar to generated source for ICU4J

Future changes will include ICU4J classes as public APIs
(still beneath android.icu). To generate these docs source
code will be needed under the expected package (android.icu),
as well as the ability to apply changes to the javadoc
comments programatically so ICU can be upgraded easily.

A consequence of this change is that libcore code can now
depend on icu in the android.icu package and not the
com.ibm.icu package as was the case previously. A nice
side effect is that the source code is available for use
during debugging as well.

Bug: 22023363
Change-Id: Icba5668fae53e2dc98ccc74e2f1ad1ca226e5feb
19 files changed