Fix data checksum processing for temp relations and dropped databases

Hi,

While reading the data checksum code, I found that BuildRelationList()
filters out non-temporary relations without storage, but does not
apply the same filtering to temporary relations. As a result, temporary
relations without storage, such as temporary views, are included in
the list of relations to wait for even though they are irrelevant to
checksum processing. For example, enabling data checksums can
unnecessarily wait for a long-lived session that owns only a temporary view.

I think BuildRelationList() should exclude temporary relations without
RELKIND_HAS_STORAGE(), matching the existing behavior for
non-temporary relations. Attached patch implements this.

Also there seems a small race condition. When enabling data checksums
online, the launcher assigns the first worker to process the shared catalogs
and prevents later workers from doing so. However, if that worker's
database is dropped after it has been selected for processing but
before checksum processing begins (a very small window), the worker
fails without processing the shared catalogs, yet they are still marked
as processed. As a result, later workers skip them, and checksum
enabling can complete successfully even though the shared catalogs
were never processed.

To fix this, we should mark the shared catalogs as processed only after
a worker completes successfully. Attached patch also implements this.

Thoughts?

Regards,

--
Fujii Masao