Unlimited dry running of the transactions

[xgreenx]

Problem overview

The executor ignores the block gas limit during the dry running of transactions. It allows the attacker to submit a lot of transactions to dry run in one request, consuming the endpoint entirely.

Solution

1. Update the executor's dry run logic to respect the block gas limit.
2. And upgrade the dry_run endpoint to deserialize transactions one by one and check that cumulative gas less than block gas limit.