Always Propose when empty_block_timeout is reached and remove redundant proposal conditions

[86667]

We now will always broadcast proposals when time_since_last_view_change > empty_block_timeout. This allows us to remove the further check on whether the exponential timeout has yet been reached when proposing (since the latter is always true if the former is true).

This means that if there are no consensus timeouts then we expect blocks to regularly be 1 seconds (+ a few ms) apart.

In timeout() Ive removed the check on has_txns() because transactions will be added to early_proposal when created and when received (if early_proposal exists). Whether there are txs in the mempool at this stage is irrelevant.

The minimum_time_left_for_empty_block variable is useful in a network in which a node is incentivised to add as many txs to their blocks as possible. Since fees are sunk in zq2 I have removed this. Happy to revert if we think it still has use.

[JamesHinshelwood]

@86667 Did you want to rebase this at some point so we can review and merge it? It looks like a good simplification of the code :)

[86667]

@86667 Did you want to rebase this at some point so we can review and merge it? It looks like a good simplification of the code :)

Definitely! It hasn't been forgotten - I am prioritising deposit contract work first so we can get the audit done asap.

[github-actions]

Bencher Report

Branch	rm_redundant_propose_conditions
Testbed	self-hosted

Click to view all benchmark results

Benchmark	Latency	Benchmark Result nanoseconds (ns) (Result Δ%)	Upper Boundary milliseconds (ms) (Limit %)
process-empty/process-empty	📈 view plot 🚷 view threshold	8.41 (-7.96%)	10.40 (80.85%)
produce-full/produce-full	📈 view plot 🚷 view threshold	1,730.90 (-16.18%)	2,737.42 (63.23%)

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