For e2e testing, figure out a way to guarantee multiple transactions are assembled together in a block

[sklppy88]

          Creating a new issue to figure out an interaction guaranteeing transactions make it in a specific block, or in the same block together. This is to address the case of different transactions not being put in the same block, even when run as a concurrent call, thus not allowing for testing a full tree (or even messages > max number of L1 -> L2 messages per tx) as right now putting in more than 1 transaction per block is doable on local, but not on CI.

Originally posted by @sklppy88 in #4899 (comment)

Look for TODO (#5104) in code