Make .eth token ID change when fuses are burned

[Arachnid]

In order to eliminate the risk of a frontrunning attack that burns fuses on a name just prior to transfer, this design changes the token ID when a fuse is burned - burning the old token and issuing a new one representing the name with the fuse burned.

Doing this breaks the assumption that token IDs are the keccak256 hashes of names, so we have to make a few changes:

• The RegistryDatastore masks out the lower 32 bits of all IDs on storage and retrieval; two keys that differ only in these bits are treated as the same key.
• Registries are now free to use these bits to store values that should form part of the identity of the name (eg, fuses/flags or a sequence ID).
• The .eth registry stores the subregistryLocked and resolverLocked fuses in the lower 2 bits of the ID.
• We change a bunch of functions, events and errors to take token IDs instead of unhashed labels: AccessDenied, InvalidSubregistryFlags, InvalidResolverFlags, renew, lock, setSubregistry.
• For ETHRegistry.register, we separate out the flags and expiration date into separate fields.
• Added the missing setResolver method.