Camera2: Make static_camera_characteristics const.

Disallow modification to static characteristics structure, and clarify
ownership and lifetime of the structure.

Also update test code accordingly.

Bug: 6243944
Change-Id: I6921d6889937212867efb99aa3881ab3ffc4f6f9
diff --git a/include/hardware/camera_common.h b/include/hardware/camera_common.h
index 5459b6c..5697bda 100644
--- a/include/hardware/camera_common.h
+++ b/include/hardware/camera_common.h
@@ -135,7 +135,9 @@
 
     /**
      * The camera's fixed characteristics, which include all camera metadata in
-     * the android.*.info.* sections.
+     * the android.*.info.* sections. This should be a sorted metadata buffer,
+     * and may not be modified or freed by the caller. The pointer should remain
+     * valid for the lifetime of the camera module.
      *
      * Version information (based on camera_module_t.common.module_api_version):
      *
@@ -150,7 +152,7 @@
      *    otherwise.
      *
      */
-    camera_metadata_t *static_camera_characteristics;
+    const camera_metadata_t *static_camera_characteristics;
 };
 
 typedef struct camera_module {