Changing `memory` option to limit resident memory instead of virtual memory, in config file and fdbserver/fdbbackup/fdbcli command-line argument. Since `rlimit` doesn't support limiting virtual memory, the current implementation have both of fdbmonitor and the fdbserver/fdbbackup process checking process RSS periodically and kill and restart the process if the limit is exceeded.
Adding a new `memory_vsize` option to limit virtual memory, if backward-compatible behavior is desired.
closes#6671, closes#6672