Allow disabling tombstone gc on a per-query basis for mutation queries.
This is achieved by a bool flag passed to mutation query variants like
`query_mutations_on_all_shards()` and `database::mutation_query()`,
which is then propagated down to compaction_mutation_state.
The future user (in the next patch) is the SELECT * FROM
MUTATION_FRAGMENTS() statement which wants to see dead partitions
(and rows) when scanning a table. Currently, due to garbage collections,
said statement can miss partitions which only contain
garbage-collectible tombstones.
Into total and live. Currently only live (those with live content) are
counted. Report live and total seprately, just like we do for rows. This
allows deducing the count of dead partitions as well, which is
particularly interesting for scans.
Closesscylladb/scylladb#26548
So tombstones can be purged correctly based on the tombstone gc mode.
Currently if repair-mode is used, tombstones are not purged at all,
which can lead to purged tombstone being re-replicated to replicas which
already purged them via read-repair.
This is not a correctness problem, tombstones are not included in data
query resutl or digest, these purgable tombstone are only a nuissance
for read repair, where they can create extra differences between
replicas. Note that for the read repair to trigger, some difference
other than in purgable tombstones has to exist, because as mentioned
above, these are not included in digets.
Fixes: scylladb/scylladb#24332Closesscylladb/scylladb#26351
The query namespace is used for symbols which span the coordinator and
replica, or that are mostly coordinator side. The querier is mainly in
this namespace due to its similar name, but this is a mistake which
confuses people. Now that the code was moved to replica/, also fix the
namespace to be namespace replica.
It belongs there, it is a completely replica-side thing. Also take the
opportunity to rename it to multishard_query.{hh,cc}, it is not just
mutation anymore (data query is also implemented).
