Fixes#20717
Enables abortable interface and propagates abort_source to all s3 objects used for reading the restore data.
Note: because restore is done on each shard, we have to maintain a per-shard abort source proxy for each, and do a background per-shard abort on abort call. This is synced at the end of "run()".
Abort source is added as an optional parameter to s3 storage and the s3 path in distributed loader.
There is no attempt to "clean up" an aborted restore. As we read on a mutation level from remote sstables, we should not cause incomplete sstables as such, even though we might end up of course with partial data restored.
Closesscylladb/scylladb#21567
* github.com:scylladb/scylladb:
test_backup: Add restore abort test case
sstables_loader: Make restore task abortable
distributed_loader: Add optional abort_source to get_sstables_from_object_store
s3_storage: Add optional abort_source to params/object
s3::client: Make "readable_file" abortable
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