Add <uses-library> information.

The required <uses-library> "androidx.camera.extensions.impl" is in the
manifest for CameraExtensionsProxy. It is necessary to explicitly add it
to `optional_uses_libs` because Soong cannot figure it out automatically
(it is not among the app dependencies, it is not an SDK library, and it
is optional).

Bug: 132357300
Test: m out/soong/.intermediates/frameworks/base/packages/services/CameraExtensionsProxy/CameraExtensionsProxy/android_common/manifest_check/AndroidManifest.xml
Change-Id: I93a7a060259569c41dfe0b88ad05c497cce6063e

packages/services/CameraExtensionsProxy/Android.bp

@@ -18,6 +18,7 @@ android_app {
     name: "CameraExtensionsProxy",
     srcs: ["src/**/*.java"],
     libs: ["androidx.camera.extensions.stub"],
+    optional_uses_libs: ["androidx.camera.extensions.impl"],
     platform_apis: true,
     certificate: "platform",
 }