JS Consumer leader step-down if underlying stream peer inactive

[tbeets]

In a scenario where a JS Consumer leader peer senses that the underlying stream peer (same server) is no longer participating in a stream peer group (for whatever reason), the consumer leader peer should step-down to transition consumer leadership to an active stream peer to insure delivery of new messages published to stream.

Server version 2.9-beta.12.

[derekcollison]

How would this be determined?