Progress monitoring for snapshot restores

[shikhar]

Restoring large indexes can be slow, e.g. we have a 450G index with lots of shards that takes an hour to restore. It would be helpful to have a way to montior progress in Kopf built on top of the endpoints that provide % measures on shard-level restore progress (https://www.elastic.co/guide/en/elasticsearch/reference/current/modules-snapshots.html#_monitoring_snapshot_restore_progress).

[lmenezes]

@shikhar currently busy trying to make kopf work correctly with 2.0. After that, this could be nice to have :)

[yehosef]

+1

[konstantin-pasko]

+1