Add block information in error context of WAL REDO apply loop

Add block information in error context of WAL REDO apply loop

Providing this information can be useful for example when diagnosing
problems related to recovery conflicts or for recovery issues without
having to go through the output generated by pg_waldump to get some
information about the blocks a WAL record works on.

The block information is printed in the same format as pg_waldump.  This
already existed in xlog.c for debugging purposes with -DWAL_DEBUG, so
adding the block information in the callback has required just a small
refactoring.

Author: Bertrand Drouvot
Reviewed-by: Michael Paquier, Masahiko Sawada
Discussion: https://postgr.es/m/c31e2cba-efda-762c-f4ad-5c25e5dac3d0@amazon.com