Update block gas allocation related to L1 messages

[greged93]

This appears to be an inefficiency as it unnecessarily constrains the amount of gas that can be consumed per block and is also inaccuratee accounting. Should we open an issue to consider modifying this behaviour in a future protocol upgrade?

Originally posted by @frisitano in #333 (comment)

[greged93]

Modify the behavior of the ScrollPayloadBuilder to avoid counting the whole gas limit of L1 messages as gas used, allowing more efficiently fill the block.