Bundle.getString(fake-signature) silently returns null when GmsCore
declares the cert via android:resource=@string/fake_signature — the
Bundle entry is an Integer (resource ID), not a String.
Add getFakeSignature() which falls back to meta.getInt() and resolves
the resource ID by loading the APK via ApkAssets.loadFromPath() +
AssetManager.Builder, avoiding re-entry into PackageManager.
requestsFakeSignature() and mayFakeSignature() now delegate to this
helper instead of calling getString() directly.
be30c1affe