eip6800: add concurrent execution information

[gballet]

Modifies the stateless witness to mark each stem with a transaction access bitmap. This bitmap is used by the client to run compatible transactions concurrently.

[g11tech]

awesome, once could construct partial order chains using this for parallel execution

[jsign]

I'm not yet convinced about the utility of this change for the following reasons:

• The EVM execution today isn't a bottleneck in verifiers.
• In the Verkle fork, we aren't planning to 10x the gas limit or similar, which can change the above bullet assumption.
• The end game is SNARKifying L1, so this will eventually become irrelevant.

If we 10x the gas limit or similar in a future fork after Verkle, then maybe it will make sense at that point if we have proof that ELs would have a speedup benefit that justifies by increasing the witness size or impl complexity for something that will be abandoned long-term.

[gballet]

To be clear, I'm not thinking of this for Osaka. It should de defined as a different upgrade. I'm thinking of a better way of doing this anyways, I'll redo the proposal then.