44564: colexec: clean up memory infra on panic in NewColOperator r=yuzefovich a=yuzefovich

It is possible that an unexpected error occurs during NewColOperator
call after we have created some memory monitoring infrastructure. In
order to correctly clean up the infra in such scenario we will now have
a separate panic catcher that closes the infra within NewColOperator.
We will also now clean up the infra when an error occurs.

Release note: None

44615: storage: remove preemptive snapshots r=tbg a=ajwerner

This commit adds a migration to remove any remaining on-disk pre-emptive
snapshots and then excises the concept from the codebase.

There's some cruft in replica_init that I'd love to clean up but don't
have a clear vision of how.

Release note: None

44660: colexec: reject CASE operator with Bytes output type r=yuzefovich a=yuzefovich

Currently, there is a contradiction between the way CASE operator
works (which populates its output in arbitrary order) and the flat
bytes implementation of Bytes type (which prohibits sets in arbitrary
order), so we reject such scenario to fall back to row-by-row engine.

Fixes: #44624.

Release note: None

44687: cli: add system.namespace_deprecated to debug zip r=knz a=otan

As we are migrating system.namespace from system.namespace_deprecated in
20.2, it may be useful to have a zip of this old table, in case it comes
in handy for debugging in future.

Release note: None

Co-authored-by: Yahor Yuzefovich <yahor@cockroachlabs.com>
Co-authored-by: Andrew Werner <ajwerner@cockroachlabs.com>
Co-authored-by: Oliver Tan <otan@cockroachlabs.com>