Task manager task covering compaction group major
compaction.
Uses multiple inheritance on already existing
major_compaction_task_executor to keep track of
the operation with task manager.
Closes#14271
* github.com:scylladb/scylladb:
test: extend test_compaction_task.py
test: use named variable for task tree depth
compaction: turn major_compaction_task_executor into major_compaction_task_impl
compaction: take gate holder out of task executor
compaction: extend signature of some methods
tasks: keep shared_ptr to impl in task
compaction: rename compaction_task_executor methods
320159c409