Modify audio-framework-aconfig as aconfig_declarations_group module type

audio-framework-aconfig module is used to provide the generated srcjar
files to the combined list located in frameworks/base/AconfigFlags.bp.

Given that the list is now being replaced with
aconfig_declarations_group module type for the ease in management, the
list can no longer accept a filegroup of srcjar files. To maintain the
current data flow of providing the list of java_aconfig_library modules,
this change modifies the module type of audio-framework-aconfig from
filegroup to aconfig_declarations_group.

Test: m api-stubs-docs-non-updatable
Bug: 320492079
Merged-In: Iab5a580ca87f2b9ff0441a1b374f3ee59a521954
Change-Id: Iab5a580ca87f2b9ff0441a1b374f3ee59a521954