Is content of the pg_autovacuum saved when pg_dumpall is used to backup the database?
pg_dumpall is simply a wrapper around pg_dump. It notes farther down in the documentation for the -n --schema flag that it only dumps non-system schemas.


  Dump only schemas matching schema; this selects both the schema itself, and all its contained objects. When this option is not specified, all non-system schemas in the target database will be dumped.


The system level things that pg_dumpall dumps instead of pg_dump are listed at the top of the pg_dumpall documentation, as you quoted above, which doesn't include a mention of system catalog tables. 

So it shouldn't actually dump out the contents of pg_catalog.pg_autovacuum. 

Which is actually a good thing. The system catalog tables are an intimate part of each PostgreSQL database, and automatically generated for you when you do a CREATE DATABASE. Their entries generally only make sense within the context of the database they were created in.

Additionally, pg_catalog.pg_autovacuum was last seen in the 8.1 to 8.3 releases of PostgreSQL, all of which have been unsupported since at least February 2013, so hopefully this is part of a migration path to a newer supported release.