serialize_collection_mutation() copies the serialized collection into
the returned collection_mutation object. Change to move to avoid the
copy.
Fixes: SCYLLADB-1041
Closesscylladb/scylladb#29010
As requested in #22104, moved the files and fixed other includes and build system.
Moved files:
- combine.hh
- collection_mutation.hh
- collection_mutation.cc
- converting_mutation_partition_applier.hh
- converting_mutation_partition_applier.cc
- counters.hh
- counters.cc
- timestamp.hh
Fixes: #22104
This is a cleanup, no need to backport
Closesscylladb/scylladb#25085