The logic of penalizing canisters for full execution and distributing
the priority across the subnet has been moved to the end of the round.
This change is necessary for priority-based eviction.

Newly created canisters join the first execution round with
an accumulated priority of zero, which breaks two existing tests,
but is not a practical issue. To compensate for this, during the reset
round, we set the accumulated priority to the canister's compute
allocation instead of the default zero priority.