the callers of the constructor does not move variable into this
parameter, and the constructor itself is not able to consume it.
as the parameter is a vector while `compaction_sstable_registration`
use an `unordered_set` for tracking the sstables being compacted.
so, to avoid creating a temporary copy of the vector, let's just
pass by reference.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#14661
3a67c31df0