check_recency: improve templates, use when reading from Promise

check_recency: improve templates, use when reading from Promise

This completes (?) the improvements to check_recency, such that it now
can force new writes to be "seen" if we are reading from an "old"
Promise too many times in a row.

mpmc-queue-noinit now runs to completion (with ASSERT() enabled):

  $ time ./run.sh mpmc-queue/mpmc-queue-noinit -f 10 -m 2
  + mpmc-queue/mpmc-queue-noinit -f 10 -m 2
  ******* Model-checking complete: *******
  Number of complete, bug-free executions: 119828
  Number of redundant executions: 38743
  Number of buggy executions: 0
  Number of infeasible executions: 344469
  Total executions: 503040
  Total nodes created: 7585797

  real	2m29.674s
  user	2m18.269s
  sys	0m10.929s