The round was usable to build the current clock in an accumulated
fashion, relative to the previous round. The end time is the absolute
metric of it, which can be used to calculate the round number (with all
previous end times).
Substrate now builds off the best block, not genesis, using the end time
included in the justification to start its machine in a synchronized
state.
Knowing the end time of a round, or the round in which block was
committed to, is necessary for nodes to sync up with Tendermint.
Encoding it in the commit ensures it's long lasting and makes it readily
available, without the load of an entire transaction.
By claiming File, they're not sent ovber the P2P network before they
have a justification, as desired. Unfortunately, they never were. This
works around that.
The BasicQueue returned obscures the TendermintImport struct.
Accordingly, a Future scoped with access is returned upwards, which when
awaited will create the machine. This makes creating the machine
optional while maintaining scope boundaries.
Is sufficient to create a 1-node net which produces and finalizes
blocks.
Multiple traits exist to verify/handle blocks. I'm unsure exactly when
each will be called in the pipeline, so the easiest solution is to have
every step run every check.
That would be extremely computationally expensive if we ran EVERY check,
yet we rely on Substrate for execution (and according checks), which are
limited to just the actual import function.
Since we're calling this code from many places, it makes sense for it to
be consolidated under TendermintImport.
