Add support for sysprop description files to Java

From now on, a java shared library can be built only with adding
".sysprop" description file to srcs. Sysprop library generator will
automatically generate a .java file, and soong will wrap it into .srcjar
file which will finally be contained in the java library. For the schema
of description file, see system/tools/sysprop/sysprop.proto.

Bug: 80125326
Test: 1) write a .sysprop description file.
2) create java_library and add description file to srcs.
3) create a test app, link against library of 2), and call generated
sysprop methods.
4) see compile succeeded.

Change-Id: I3ff87bc0a20f5a1aa126ef6d0f4d874a2ff4af8d