Today, compaction is calling compaction manager to register / deregister
the compaction_info created by it.
This is a layer violation because manager sits one layer above
compaction, so manager should be responsible for managing compaction
info.
From now on, compaction_info will be created and managed by
compaction_manager. compaction will only have a reference to info,
which it can use to update the world about compaction progress.
This will allow compaction_manager to be simplified as info can be
coupled with its respective task, allowing duplication to be removed
and layer violation to be fixed.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>