Surface Java APIs Used By APK-only Modules.

Previously we were only generating used-by API-coverage for APEX modules.
This change adds support for APK-only modules such as NetworkStack and DocumentsUI.

Bug: b/216313756
Forrest Run: https://android-build.googleplex.com/builds/abtd/run/L10800000953846781

Test: TARGET_BUILD_VARIANT=userdebug PRODUCT=mainline_modules_x86 ./vendor/google/build/build_unbundled_coverage_mainline_module.sh -j16

Change-Id: Id17e4a55c2a52e9903632a654e778f8d54982dfc
Merged-In: Id17e4a55c2a52e9903632a654e778f8d54982dfc
(cherry picked from commit 56d75785bd52c8a8f684935eed67fceb2c0e6850)
diff --git a/java/testing.go b/java/testing.go
index 82aa29b..9178b16 100644
--- a/java/testing.go
+++ b/java/testing.go
@@ -54,6 +54,8 @@
 		"build/soong/java/lint_defaults.txt": nil,
 		// Needed for apps that do not provide their own.
 		"build/make/target/product/security": nil,
+		// Required to generate Java used-by API coverage
+		"build/soong/scripts/gen_java_usedby_apex.sh": nil,
 	}.AddToFixture(),
 )