switch/nrt: add infrastructure to support job suspend/resume

switch/nrt: add test for ability of job to be suspended

Adds most of the infrastructure to the switch plugin for suspend APIs

still need to flesh out the functions for switch/nrt and add support to
new RPC in slurmd.

switch/nrt: and un/pack and use of switch info for job suspend/resume

Major re-write of switch plugin web page for new job preemption functions

switch/nrt: add more logging for job suspend/resume

switch/nrt: document long-term job suspension support on web page