fix(batcher): Register last submitted batch block when batcher is initialized

[PatStiles]

Upon initialization the batcher currently fetches the last block from an rpc node by invoking the getBlockNumber JSON-RPC call. Ideally we should register the last submitted batch block and reference it upon initialization.

ref: https://github.com/yetanotherco/aligned_layer/blob/staging/batcher/aligned-batcher/src/lib.rs#L254