allow to configure retain_height of CometBFT blocks

[tzemanovic]

In ABCI Commit response we currently return 0 for retain_height which means no pruning. We could allow to configure this per node, but by default it should be set to no pruning: "If all nodes in the network remove historical blocks then this data is permanently lost, and no new nodes will be able to join the network and bootstrap, unless state sync is enabled on the chain. Historical blocks may also be required for other purposes, e.g. auditing, replay of non-persisted heights, light client verification, and so on." (excerpt from CometBFT docs)