centralize constants in one file

[entropidelic]

We have constants scattered along many files. It will be useful and make the code much cleaner if we had constants in one file and read them from there. If one file is too much work, we could have at least one per entity e.g., batcher, operator, aggregator, etc. Some example constants:

• Rust gas costs
• contract addresses in make
• other number constants in make
• contract addresses to deploy batcherPayments
• retries and wait times