feat!: var output estimation optimization

[segfault-magnet]

closes: #1380 The number of variable outputs is now determined by filling the dry-run tx with as much variable outputs as the node will allow (consensus_params.tx_params.max_ouputs - whatever other outputs are already present) and counting the number of TransferOut receipts made by the dry run.

I've checked with the core devs, ideally we'd be looking at the tx outputs themselves but since the dry run endpoint doesn't return a tx this is the next best thing since only TRO instructions require a variable output attow.

Breaking changes

• .append_variable_outputs(n) is replaced by .with_variable_output_policy(VariableOutputPolicy::Exactly(n)).

• .estimate_tx_dependencies(max_attempts) has been replaced with .determine_missing_contracts(max_attempts) and will only add the missing contract inputs and no longer estimate variable outputs. To estimate variable outputs you should now add .with_variable_output_policy(VariableOutputPolicy::EstimateMinimum)

Checklist

• [x] I have linked to any relevant issues.
• [x] I have updated the documentation.
• [x] I have added tests that prove my fix is effective or that my feature works.
• [x] I have added necessary labels.
• [x] I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• [x] I have requested a review from the relevant team or maintainers.

[hal3e]

Regarding the naming: with_variable_output_policy is good. However, determine_missing_contracts could be misleading because we will determine them and add them to the outputs. So maybe something like fix_missing_contracts or determine_and_update_missing_contracts ...

[digorithm]

Regarding the naming: with_variable_output_policy is good. However, determine_missing_contracts could be misleading because we will determine them and add them to the outputs. So maybe something like fix_missing_contracts or determine_and_update_missing_contracts ...

Yeah, I was (and maybe still am) on the fence about determine_missing_contracts. Maybe just update_missing_contracts? update indicates it will mutate the inner stuff and also does some magic underneath.

[segfault-magnet]

Thing is previously it was called "estimate_tx_dependencies" that also didn't have anything claiming mutability.

I share the concern but have no satisfactory name that isn't a kilometer long.

maybe discover_missing_contract_inputs ?