Camera: Reduce unnecessary expanding of characteristics metadata

Camera service adds and modifies certain camera characteristics keys.
That has the adverse side effect of doubling the memory footprint of
the camera characteristics objects.

Reduce the chance of such side effect by reserving extra entries and
data count during initialization.

Flag: com.android.internal.camera.flags.metadata_resize_fix
Test: Observe heap profile of cameraserver in idle
Bug: 379388099
Change-Id: I4a4dc236e2afc26f2b958dd8f78b8096faa4d632