Move init-api rule srcs to a subpackage, init.api

Previously, the only way to see the boundary between the init-base
package and -api was to look at the list of srcs. Putting a package
boundary between them makes it easier to understand without reading
the BUCK file.

Change-Id: I2ccb43cc9154b6979a867b01b4e3ea86070dc30f
36 files changed