## Description 

Mostly based on https://github.com/MystenLabs/sui/pull/18009.

Info contained in blocks can get outdated quickly, but processing old
blocks still take significant resources. Disable proposing new blocks if
there is no active peer consumer.

## Test plan 

CI
Private testnet

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## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] Indexer: 
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK: