Collect aconfig_declarations of the dependent java_aconfig_library modules

droidstubs module require aconfig_declarations modules to be specified
when the module depends on the java_aconfig_library module in order to
generate the "exportable" stubs. This adds burden to the droidstubs or
java_sdk_library module owners, as module should specify both the
java_aconfig_library and aconfig_declarations modules to genreate the
"exportable" stubs, although the necessary information from the
aconfig_declarations module can be provided from the
java_aconfig_library modules.

In order to resolve such burden, this change enables the intermediate
cache files from the associated aconfig_declarations module of a
java_aconfig_library module to be propagated to its reverse dependencies
without having the specify the aconfig_declarations modules in the
droidstubs or java_sdk_library modules definitions.

This does not mean that the intermediate cache files of every transitive
dependencies of the java_sdk_library or the droidstubs will be passed to
aconfig to retrieve the state of the aconfig flags.

Specifically, only the java_aconfig_library modules or the java_library
modules that have static dependency on java_aconfig_library modules that
are passed to droidstubs via `libs` or `srcs` (using
":module_name{.tag}" syntax) will provide the intermediate cache files
to generate the "exportable" stubs. For java_sdk_library, all modules
listed as `libs`, `static_libs`, `stub_only_libs`, and `apiScope.libs`
are passed as `libs` and all modules listed as `api_srcs` and `srcs` are
passed as `srcs` to the droidstubs modules dynamically generated in
java_sdk_library module per api scope, thus these properties will be
affected.

Note that the test is being added in the apex package. This is because
trying to register the codegen package build components in the java
package leads to circular dependency between the codegen and the java
package, as codegen package imports the java package.

Test: m nothing --no-skip-soong-tests
Bug: 329284345
Change-Id: I7953ab64776f6947808321ce8a3598154501bcfe