Camera: Enable instant access to camera extension proxy service

Instant apps must be able to communicate with the camera extension
proxy service.

Bug: 199695516
Test: atest -c --instant
cts/tests/camera/src/android/hardware/camera2/cts/CameraExtensionCharacteristicsTest.java
atest -c --instant
cts/tests/camera/src/android/hardware/camera2/cts/CameraExtensionSessionTest.java

Change-Id: Ibf6adaf4746456fd88656e894a1d9ea45a7b07cc