move proof building before root computation

[gballet]

This is a rewrite of #517. It generates the proof against the prestate, before the post state is inserted. This avoids reloading the prestate from disk.

TLDR: Break the proving into two parts:

1. the Proof part where the proof is build, which is called before IntermediateRoot
2. the "post state" part, which is created after the intermediate root has been computed.

In the case of the execusion spec test, the pre tree is saved before execution, so there is no need to move things around, just use the new API.

[jsign]

Makes sense, but note the CI is failing.

[Copilot]

Copilot reviewed 4 out of 4 changed files in this pull request and generated no suggestions.

Comments skipped due to low confidence (2)

cmd/evm/internal/t8ntool/execution.go:374

• [nitpick] The function name 'Proof' is not very descriptive. Consider renaming it to 'GenerateProof'.

proof, err := trie.Proof(vtrpre, proofTrie, keys, vtrpre.FlatdbNodeResolver)

cmd/evm/internal/t8ntool/execution.go:378

• [nitpick] The error message 'error adding post values to proof' could be more descriptive. Consider including more context about what went wrong.

err = trie.AddPostValuesToProof(keys, proofTrie, proof)