Camera: Support lazy HALs

Drop camera HAL references when unused.

Use ro.camera.enableLazyHal property to toggle behavior on or off.
 * If true, the cameraserver drops references to ICameraProvider HALs
   when they are not being used for either camera or torch.
 * If false (or unset), stores a strong reference to each ICameraProvider
   that is registered. This is the same as the old behavior.

Bug: 79374634
Test: Apply CL that lets camera HAL exit when unused. Open camera/enable
      torch, close camera/disable torch, check ps -A to see if HAL exits.
Change-Id: I1842f9bf9e862ab74e4ec8aa72fc46fc47782ed0