Move ifname to slurm_opt_t, rather than keeping it in sbatch_opt_t
and srun_opt_t, making the arg handling code much simpler.

Skip setting it to /dev/null as part of the reset, and move that logic
to _opt_verify().

Fix a mistake in the API in slurm_get_job_stdin() where StdIn= is
prepended to /dev/null if ifname == NULL.

Move efname to slurm_opt_t, rather than keeping it in sbatch_opt_t
and srun_opt_t, making the arg handling code much simpler.

Since 'sleep' is what will be executed, the correct JobName is sleep.

For sbatch - first_pass() is an explicitly separate phase, and will
clear the struct for us. Every successive call should feed in 'false'
to prevent sbatch_early_pass settings - like quiet / verbose - from
getting overwritten.

And some further cleanup now that all option parsing code is moved to
slurm_opt.c.

Move all logic for setting defaults and setting the name across
HetJob components in to _match_job_name().

Remove JOB_SALLOC_FLAG, and default_job_name from salloc_opt_t.

Just check if sentinel value of NO_VAL is still set instead.

Just check if sentinel value of NO_VAL is still set instead.

While here, drop test on SLURM_STARTED_STEP envvar which is never
set (was used with POE), and move this logic to _opt_verify().

Note that sbatch intentionally handles this in a different way -
it injects the file contents into the job script, rather than
sending it in burst_buffer in job_desc_msg_t.

Replace three implementations of _read_file() with create_mmap_buf().

Use _unknown_ as the name here, since ? is obviously invalid.

Drop egid from slurm_opt_t in favor of simpler handling of gid itself.

Drop euid from slurm_opt_t in favor of simpler handling of uid itself.

Note symbol hack to permit the help() functions to stay in place within
the commands for now.

Drop -u as an option for salloc/sbatch, since srun has it for --unbuffered.

Note symbol hack to permit the usage() functions to stay in place within
the commands for now.

All salloc environment variables are now being handled through
slurm_process_option().

Note one important difference: this delays processing of --hint until
the verify pass, at which time --ntasks-per-core or --threads-per-core
may have been evaluated. Previously, order of argument evaluation would
change the result, despite a comment on each of these warning against
such behavior.

Also switch the order of SLURM_HINT and SBATCH_HINT - SBATCH_HINT will
now override SLURM_HINT if both are set.

Handle the two separated envvars here as well.

Drop option from srun, as it just prints an error.

Set the default value to 0, and use that to indicate if set rather
than tracking a separate kill_command_set variable in salloc_opt).

Use slurm_option_set_by_env() in srun in one location, and remove
network_set_env from srun_opt_t.

Drop the direct SLURM_NETWORK envvar set in the srun option parsing -
this was duplicated further below for Cray systems (the only ones using
this variable) in _opt_args() and thus can be removed here.

Get rid of job_name_set_cmd/job_name_set_env in srun_opt_t and use
slurm_option_set_by_cli()/slurm_option_set_by_env() instead.