Previous logic had an invalid pointer that could result in a segv.
Previous logic failed to properly allocate tres-per-node ot tres-per-job
without defining gres topology information

rather than just report GRES_IDX (index) info, report GRES count
info as well, since it can vary from node-to-node with cons_tres

This fixes a couple of bugs related to allocating GRES when
there is no associated topology, including adding support for
the --tres-per-job option

for current cons_tres testing and future use

Enforce configured default values for DefMemPerGPU
and DefCPUPerGPU

spread a job over multiple nodes if needed to
satisfy mem-per-gpu specification

Force job to span nodes when appropriate

The last bit of logic to talk with the GPUs is still needed

this includes a new regression test

This fixes a couple of bugs in commit 0e4874e19490a24
1. round up core count for job as needed (i.e. if job needs 3
   CPUs per task and there are 2 CPUs per core, the job needs
   2 cores rather than 1)
2. fix some bad logic of available cores on socket 0 is 0
3. failed to set exit_code to 1 on a expect test failure

correction to logic for explicit hostname specification on job submit
bug introduced in commit 0e4874e19490a24fb54961ef89176a3e8f55952b

also add a regression test for this scheduling logic
bug 4584

Add that desired GPU count is actually allocated to a job based upon
--gpus, --gpus-per-node, --gpus-per-socket, and --gpus-per-task
options

this bug exists with all select plugins. if a job has been allocated
gres and the gres have either topology or type information and the
slurmctld daemon restarts (while the job is running), then when the
job ends gres underflow errors will be generated. the problem is
due to the slurmctld not having gres topology or type information
available at restart time so that it can not update counters. the
overhead of updating those counters at node registration time is
high, so we just avoid generating the errors in this case.
note: this bug is not specific to cons_tres and  exists in
earlier versions of slurm.

if the step does not explicity specify a gres-per-node value,
then the step will be allocated gres identical to that allocated
to the job

also relocate tres_mc create/destroy location so information can be
access from additional locations and to reduce overhead of creating
it multiple times

it is not going to work in practice

Modify gres_plugin_job_alloc() to allocate pre-selected GRES.
Add fields to job GRES data structure to define selected GRES
before job allocation time.