Add non-text output formats to pg_dumpall

Add non-text output formats to pg_dumpall

pg_dumpall can now produce output in custom, directory, or tar formats
in addition to plain text SQL scripts. When using non-text formats,
pg_dumpall creates a directory containing:
- toc.glo: global data (roles and tablespaces) in custom format
- map.dat: mapping between database OIDs and names
- databases/: subdirectory with per-database archives named by OID

pg_restore is extended to handle these pg_dumpall archives, restoring
globals and then each database. The --globals-only option can be used
to restore only the global objects.

This enables parallel restore of pg_dumpall output and selective
restoration of individual databases from a cluster-wide backup.

Author: Mahendra Singh Thalor <mahi6run@gmail.com>
Co-Author: Andrew Dunstan <andrew@dunslane.net>
Reviewed-By: Tushar Ahuja <tushar.ahuja@enterprisedb.com>
Reviewed-By: Jian He <jian.universality@gmail.com>
Reviewed-By: Vaibhav Dalvi <vaibhav.dalvi@enterprisedb.com>
Reviewed-By: Srinath Reddy <srinath2133@gmail.com>

Discussion: https://postgr.es/m/cb103623-8ee6-4ba5-a2c9-f32e3a4933fa@dunslane.net