Integrated restore

[kreuzerkrieg]

Handed over from https://github.com/scylladb/scylladb/pull/20149

This adds minimal implementation of the start-restore API call.

The method starts a task that runs load-and-stream functionality against sstables from S3 bucket. Arguments are:

endpoint -- the ID in object_store.yaml config file
bucket -- the target bucket to get objects from
keyspace -- the keyspace to work on
table -- the table to work on
snapshot -- the name of the snapshot from which the backup was taken

The task runs in the background, its task_id is returned from the method once it's spawned and it should be used via /task_manager API to track the task execution and completion.

Remote sstables components are scanned as if they were placed in local upload/ directory. Then colelcted sstables are fed into load-and-stream.

This branch has https://github.com/scylladb/scylladb/pull/19890 (Integrated backup), https://github.com/scylladb/scylladb/pull/20120 (S3 lister) and few more minor PRs merged in. The restore branch itself starts with utils: Introduce abstract (directory) lister commit.

refs: https://github.com/scylladb/scylladb/issues/18392