cl/pool: Derive operation pool sizes from BeaconChainConfig

[phrwlk]

This change replaces the hardcoded pool capacity with values derived from BeaconChainConfig, matching OperationPool’s documented expectation that capacity is computed as the per-block maximum times an internal multiplier. Previously, NewOperationsPool accepted a BeaconChainConfig but ignored it, which contradicted the presence of per-block operation limits in the config and undermined capacity sizing semantics. The new code computes per-pool capacities from the corresponding Max* fields, taking the maximum across pre- and post-fork values where applicable to avoid undersizing across upgrades. This improves correctness and observability, ensures pool sizes reflect network parameters, and removes the stale constant without altering downstream logic or test expectations beyond sizing.