Add support for @.jcite references in srcgen

Convert {@.jcite .... to Doclava's {@sample .... format.

Generate source code for ICU4J sample code repackaged to
android.icu. Only some of the ICU4J samples are repackaged:
the aim is to compile these against the latest APIs once they
become public.

The android.icu.util.Output class has been added to the public API
as it is required to use them.

Refactoring of currysrc / srcgen to avoid some code duplication.

This change also contains the regenerated android_icu4j source code.

Bug: 22023363
Change-Id: I2661041998898bafe1592522f9c9ec758c96da3b
23 files changed