Additional fixes for java_sdk_library

This change fixes several problems found while re-defining some libs
using java_sdk_library module type.

1) A phony module whose name is the same as the java_sdk_library name is
defined. It is used to support installing the runtime library via
PRODUCT_PACKAGES (even when there is no dependency from other modules).

2) A bug that package names whose depth is >= 2 is ignored in
droiddoc.srcs_lib_whitelist_pkgs is fixed. A package name foo.bar.baz is
now converted to a path foo/bar/baz following the Java convention.

3) A make variable JAVA_SDK_LIBRARIES that is the list of java_sdk_library
module names is exported to make. This can be used to distinguish SDK
libraries from ordinary libs.

4) When running doclava, some framework sources in the 'android' package
and the same packages as the SDK library are automatically added to the
sources list. This is required for the case when API class is extending
from the framework class. In that case, doclava needs to know whether
the base class is hidde nor not. Since that visibility info is encoded
as @hide string in the comment, we need source files for the classes,
not the compiled ones. Also there are rare cases where part of SDK
library is implemented in the framework (e.g. org.apache.http.legacy).
In that case, we need framework source to make API stubs, though the
sources are not required to build the runtime library.

5) The stubs libs are disabled for PDK builds as well.

Bug: 77575606
Test: m -j

Change-Id: I360cf15fe5339e46644fb16d0dabe2548aa315f9