EVM/Node: needs process L1 block is checked on [New_last_known_l1_level]

Because of another bug, we changed how the needs_process is computed in !15620 (merged).

However, I by mistake removed partialy the safety guard. The needs_process is checked only if there are events in the block, this is really stupid. The merge request reintroduces the safety guard by checking the L1 block level in the Evm_context for the request New_last_known_l1_level.

The rollup node is anyway not supposed to push old blocks on the stream anyway, I even started by removing all guards in the previous merge request. But, turns out the rollup node can have bugs as well.