Add targetGasLimit to the cluster_definition to allow the creation of clusters with higher gas targets

[OisinKyne]

🎯 Problem to be solved

The community wants to raise the target gas limit. Currently that is not easy to do in Charon.

🛠️ Proposed solution

The challenge here, is trying to coordinate all VCs to sign a higher limit. This is something we attempted early in charon development, and disfavoured over signing a single registration at the point of dkg or key splitting.

To begin, I suggest we stick to the key splitting/dkg moment, but further more realtime approaches may be considered in future.

The suggestion is to include a target_gas_limit field in a new version of the cluster_definition object. With a default of 36m. This could be overridden with the flag --target-gas-limit int The target block gas limit for the cluster (Default: 36000000)

This const https://github.com/ObolNetwork/charon/blob/main/core/validatorapi/validatorapi.go#L36 is what should be parameterized.

• Approved design doc: link
• Core team consensus on the proposed solution

Describe the solution to be implemented

🧪 Tests

• Tested by new automated unit/integration/smoke tests
• Manually tested on core team/canary/test clusters
• Manually tested on local compose simnet