The prior workflow (now deleted) required manually specifying the packages to
check and only checked the package could compile under the stated MSRV. It
didn't verify it was actually the _minimum_ supported Rust version. The new
version finds the MSRV from scratch to check if the stated MSRV aligns.
Updates stated MSRVs accordingly.
Also removes many explicit dependencies from secq256k1 for their re-exports via
k256. Not directly relevant, just part of tidying up all the `toml`s.
Cosigns was an archive of every single cosign ever received. By scoping
NetworksLatestCosignedBlock to be by the global session, we have the latest
cosign for each network in a session (valid to replace all prior cosigns by
that network within that session, even for the purposes of fault) and
automatically have the notable cosigns indexed (as they are the latest ones
within their session). This not only saves space yet also allows optimizing
evaluation a bit.
Not only cleans the existing cosign code but enables non-Serai-coordinators to
evaluate cosigns if they gain access to a feed of them (such as over an RPC).
This would let centralized services not only track the finalized chain yet the
cosigned chain without directly running a coordinator.
Still being wrapped up.
