Various raft cleanups

Including unconditional u2_lo_lead, relying on lead to differentiate
batch vs. interactive mode.
Trivial ames cleanup
Split term and sist initialization

Also remove the log conversion code and make ular sequence numbers
64-bit.
Shuffle sist around
Temporarily disable checkpointing
64-bit in raft push
Send heartbeats immediately on election
Send apen rather than beat

Now apen falls back to beat if we don't have anything to send.

Also made u2_sist_rent return n entries at a time, and made it slightly
more robust.
TEMP WIP DO NOT PUSH new restore process