Add more information for WAL records of hash index AMs

Add more information for WAL records of hash index AMs

hashdesc.c was missing a couple of fields in its record descriptions, as
of:
- is_prev_bucket_same_wrt for SQUEEZE_PAGE.
- procid for INIT_META_PAGE.
- old_bucket_flag and new_bucket_flag for SPLIT_ALLOCATE_PAGE.

The author has noted the first hole, and I have spotted the others while
double-checking this area of the code.  Note that the only data missing
now are the offsets stored in VACUUM_ONE_PAGE.  We could perhaps add
them, if somebody sees value in this data, even if it makes the output
larger.  These are discarded here.

Author: Kirill Reshke <reshkekirill@gmail.com>
Discussion: https://postgr.es/m/CALdSSPjc-OVwtZH0Xrkvg7n=2ZwdbMJzqrm_ed_CfjiAzuKVGg@mail.gmail.com