Added support for P4D r23.1+ multi-file per-table parallel checkpoints.
If DO_PARALLEL_CHECKPOINTS=4 (for example) is set in the instance vars
file, live checkpoints are created with 'p4d -jcpm' and daily
checkpoints are created with 'p4d -jdpm'. Replays are done with
'p4d -jrp' (same as in P4D r22.2; there is no '-jrpm').
With this change, live_checkpoint.sh and daily_checkpoint.sh take
advantage of parallel checkpoint features.
* Add doc coverage in SDP Guide for the full lifecycle of parallel
checkpoints, including updates to recovery procedures.
* Other checkpoint-handling scripts: