feat: move state/receipt building to new method

[meyer9]

Moves transaction processing logic of build_pending_state to a new struct. Also separates out reusing a cached execution from executing using the EVM.

This also removes block_hash from receipts and transactions which matches the spec and removes the need for calculating a useless block hash for every flashblock.

The next step is to move the for loop into this struct which will return an iterator of results.

Using this, we'll be able to prewarm accessed addresses using FALs and eventually process transactions in parallel. Moving execution to a new struct allows us to implement a trait for building flashblocks and switch out different implementations (prewarming, parallel, sequential).

[cb-heimdall]

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[refcell]

If we're going to refactor the pending logic into a struct, could we take the extra step and move it into a new module to try to make this code a bit easier to read?

[meyer9]

Yup, good idea! Made a few changes: moved the state builder it to a new state_builder module, passed tx reference to transact to avoid cloning, and removed touched_account_balances since that's duplicating EvmState that's already returned.

[refcell]

Looks great thanks @meyer9