Remote Externalities: Start downloading KVs early

[eagr]

Follow up of #1985

As described, we don't necessarily have to wait till we have collected all the keys. By starting as soon as we have collected some keys, we could potentially save a couple more minutes. I presume the benefit will increase with the growth of the total amount of KVs as it would take more time to collect all the keys.

The downside is we might not be able to show the downloading progress as we do now. But if we does manage to speed things up, I guess this is tradeoff acceptable?

CC @ggwpez @liamaharon

[ggwpez]

The downside is we might not be able to show the downloading progress as we do now.

It could have two bars i assume; one for keys and one for values.
NVM just read the other issue since we dont know the total number of KV pairs.

[liamaharon]

The downside is we might not be able to show the downloading progress as we do now. But if we does manage to speed things up, I guess this is tradeoff acceptable?

This is ok