Refactor payload builder to accept generic builder tx

[avalonche]

📝 Summary

Refactor to allow the payload builder accept generics for how to construct the builder tx.

💡 Motivation and Context

Easier to add custom logic to builder tx based on the payload builder such as contract calls etc.

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✅ I have completed the following steps:

• Run make lint
• Run make test
• Added tests (if applicable)

[avalonche]

returns empty vec for now

[avalonche]

replace with flashblocks builder tx contract call

[noot]

it'd be a lot cleaner to have this as an enum as opposed to a trait, so you don't need to use generic BuilderTransactions everywhere.

eg.

pub enum BuilderTransactions {
    Flashblocks(FlashblocksBuilderTx),
    Standard(StandardBuilderTx),
    Flashtestations(FlashtestationsBuilderTx),
}

impl BuilderTransactions {
    pub fn simulate_builder_txs(&self, ...) {
        match self {
            Self::Flashblocks(inner) => inner.simulate_builder_txs(...),
            Self::Standard(inner) => inner.simulate_builder_txs(...),
            Self::Flashtestations(inner) => inner.simulate_builder_txs(...),
        }
    }
    
    pub fn add_builder_txs(&self, ...) { ... }
    pub fn simulate_builder_txs_state(&self, ...) {...}
}

you can also get rid of the ExtraCtx generic param as well with this, as each type (FlashblocksBuilderTx, etc) can contain its own context.

[avalonche]

Sounds good but I would try the enum approach in a follow up PR to refactor the existing generic builder tx

[noot]

that would be great!