PR #93557 - syntheticprivilegecache: scan all privileges at startup

[cockroach-teamcity]

Related PR: cockroachdb/cockroach#93557
Commit: cockroachdb/cockroach@268d0f4

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Release note (performance improvement): In 22.2 we introduced privileges on
virtual tables (system catalogs like pg_catalog, information_schema, and
crdb_internal). A problem with this new feature is that we now must fetch those
privileges into a cache before we can use those tables or determine their
visibility in other system catalogs. This process used to occur on-demand, when
the privilege was needed. Now we'll fetch these privileges eagerly during
startup to mitigate the latency when accessing pg_catalog right after the
server boots up.