Introduce module type aconfig_declarations_group

In order to easily manage aconfig_declarations modules and their
corresponding codegen modules, this change introduces a new module type
`aconfig_declarations_group`. The module enables listing codegen modules
by language, and correctly depend on the desired output files using
appropriate tags.

e.g. for an aconfig_declarations_group module "some_group", the rdeps of
the module can:
- gather all intermediates cache files of the aconfig_declarations with
  ":some_group" tag.
- gather generated srcjar files of the listed java_aconfig_library
  modules with ":some_group{.srcjars}" tag.

Output tag support for cc modules and rust modules will be added in
future changes.

Test: m nothing --no-skip-soong-tests
Bug: 320492079
Change-Id: I93d737577f8d00198ed91048dd6e81ef238193cb

aconfig/codegen/init.go

@@ -77,6 +77,7 @@ func init() {
 }
 
 func RegisterBuildComponents(ctx android.RegistrationContext) {
+	ctx.RegisterModuleType("aconfig_declarations_group", AconfigDeclarationsGroupFactory)
 	ctx.RegisterModuleType("cc_aconfig_library", CcAconfigLibraryFactory)
 	ctx.RegisterModuleType("java_aconfig_library", JavaDeclarationsLibraryFactory)
 	ctx.RegisterModuleType("rust_aconfig_library", RustAconfigLibraryFactory)