Fix continuous aggregate privileges during upgrade

[erimatnor]

Copy ACL privileges (grants) from the query view (user-facing object)
to the internal objects (e.g., materialized hypertable, direct view,
and partial view) when updating the extension to the new version. A
previous change added such propagation of privileges when executing
GRANT statements, but didn't apply it retrospectively to the
internal objects of existing continuous aggregates.

Having the right permissions on internal objects is also necessary for
the watermark function used by real-time aggregation since it queries
the materialized hypertable directly.

The update script copies the ACL information from the user-facing view
of every continuous aggregate to its internal objects (including the
materialized hypertable and its chunks). This is done by direct insert
into pg_class instead of executing a GRANT statement in the update
script, since the latter will record the grant/ACL as an init
privilege (i.e., the system believes the GRANT is for an extension
object). The init privilege will prevent this ACL from being included
in future dump files, since pg_dump only includes non-init
privileges as it believes such privileges will be recreated with the
extension.

Fixes #2825

[codecov]

Codecov Report

Merging #2845 (eaed20c) into master (126f1c8) will increase coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2845      +/-   ##
==========================================
+ Coverage   90.07%   90.20%   +0.12%     
==========================================
  Files         212      212              
  Lines       34772    34722      -50     
==========================================
  Hits        31322    31322              
+ Misses       3450     3400      -50     

Impacted Files	Coverage Δ
src/loader/bgw_message_queue.c	87.09% <0.00%> (ø)
src/import/planner.c	70.30% <0.00%> (+11.12%)	⬆️

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