sql: populate pg_catalog.pg_default_acl table

[jseldess]

PR: cockroachdb/cockroach#67872

Release note:

• Populated pg_catalog.pg_default_acl. This is important for tracking which default privileges are defined in the database. pg_catalog.pg_default_acl has 5 columns:
  • oid (oid): row identifier
  • defaclrole (oid): oid of the role the default privileges are defined for
  • defaclnamespace (oid): oid of the schema the default privileges are defined in
  • defaclobjtype (char): r = relation (table, view), S = sequence, f = function, T = type, n = schema
  • defaclacl (aclitem[]): string representation of default privileges, following the format "$1=$2/$3" where $1 is the grantee's username, $2 is a list of characters representing the privileges, and $3 is the grantor (which is currently always an empty string in CockroachDB).
  Privileges are represented by chars in the aclitem[] representation.
  • CREATE = 'C'
  • SELECT = 'r'
  • INSERT = 'a'
  • DELETE = 'd'
  • UPDATE = 'w'
  • USAGE = 'U'
  • CONNECT = 'c'
  See the PostgreSQL documentation for the table of PostgreSQL-supported privileges and their char representations and the PostgreSQL definition of pg_catalog.pg_default_acl. [#67872][#67872]

[ericharmeling]

I don't think this requires updates to the docs, as this table is already marked as implemented.