AztecNode.getBlocks(0, ...) should return from genesis

If running `AztecNode::getBlocks(0, ...)` it will throw an error. While this makes sense when understanding that the genesis (block 0) is essentially the state set in the L1 contract, it feels wrong and unnecessarily clunky to make it throw. Instead i suggest that we just make it behave like starting from 1 to let `getBlocks(0, ...)` simply indicate: "give me blocks from the beginning".