libvrflinger: Add additional info to PDX dump.

- Add logging for surface and layers.
- Minor cleanup of AcquiredBuffer code.
- Add additional debug tracing.

Bug: None
Test: servicetool --dump /dev/socket/pdx/system/vr/display/client
Change-Id: Ie7cfe46978139e0eef2184b03acb4b9bab428a33