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