Updates to polkadot-v0.9.40, with a variety of dependency updates accordingly.
Substrate thankfully now uses k256 0.13, pathing the way for #256. We couldn't
upgrade to polkadot-v0.9.40 without this due to polkadot-v0.9.40 having
fundamental changes to syncing. While we could've updated tendermint, it's not
worth the continued development effort given its inability to work with
multiple validator sets.
Purges sc-tendermint. Keeps tendermint-machine for #163.
Closes#137, #148, #157, #171. #96 and #99 should be re-scoped/clarified. #134
and #159 also should be clarified. #169 is also no longer a priority since
we're only considering temporal deployments of tendermint. #170 also isn't
since we're looking at effectively sharded validator sets, so there should
be no singular large set needing high performance.
