feat: add latest_block_height and is_stable to /state; only stable nodes can partake in signature generation

[ChaoticTempest]

This adds in the latest_block_height and is_stable values to StateView so a node can keep track whether a connection is stable or not. A node will only consider another node to be able to generate a signature if and only if it is stable, such as when it is caught up with indexed blocks. This only affects signature generation, so things like triples, presginatures, resharing are still fine even if a node is not stable.

This fixes #680 partially but only handles the honest node portion.

[volovyks]

LGTM.
I was expecting that nodes would fetch other nodes' states and decide if they are active by themselves, but that approach has its downsides too.

[github-actions]

Terraform Feature Environment Destroy (dev-710)

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Pusher: @ChaoticTempest, Action: pull_request, Working Directory: ``, Workflow: Terraform Feature Env (Destroy)