Handle android_app_set in Soong built apkcerts.txt

android_app_set modules contain presigned apks, and uses `extract_apks`
to create an entry for each split apk in `LOCAL_APK_CERTS`, which then
gets concatenated to apkcerts.txt when built using Make.

This logic was previously not handled correctly in the new Soong
implementation, causing build errors in partner workspaces.

Bug: 396131789
Test: In partner-workspace, built the soong generated apkcerts.txt file
Change-Id: I7dd0dcd6c992660d5a7e7d484b5d83dc06e051f3
diff --git a/java/app.go b/java/app.go
index 560129b..8d4c3bb 100644
--- a/java/app.go
+++ b/java/app.go
@@ -82,6 +82,7 @@
 	Certificate                   Certificate
 	PrivAppAllowlist              android.OptionalPath
 	OverriddenManifestPackageName *string
+	ApkCertsFile                  android.Path
 }
 
 var AppInfoProvider = blueprint.NewProvider[*AppInfo]()