This patch adds the compaction id to the get_compaction structure.
While it was supported, it was not used and up until now wasn't needed.
After this patch a call to curl -X GET 'http://localhost:10000/compaction_manager/compactions'
will include the compaction id.
Relates to #7927
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
Closes#8186