Unify independent constants

**Task description**

There are a few constants in the network layer, in particular `PROTOCOL_MAX_MESSAGE_SIZE` and `PROTOCOL_MAX_TRANSACTION_SIZE` which should be more closely aligned with similar constants/parameters used in the scheduler/consensus.

In particular block size is now configurable indirectly via the energy parameter so ideally we'd inform max_message_size based on that.

**Sub-tasks**
- [ ] Figure out the correct way to define MAX_MESSAGE_SIZE. Note that this is important to have to prevent resource exhaustion.
- [ ] Implement

Start by tracing the network-layer constants PROTOCOL_MAX_MESSAGE_SIZE and PROTOCOL_MAX_TRANSACTION_SIZE and comparing them with the scheduler/consensus parameters and the energy-based block-size configuration. The issue names no files or tests, so first locate those entry points and determine the safe limit required to prevent resource exhaustion. Done means the independent constants are aligned and the implementation reflects the configurable block size.

Written by the indexing model from the issue text.