fix(scheduler): populate job-wide total want for per-host resources during global phase (bug-1790)

Closes the gap bug-1789 explicitly carved out: a GLOBAL limit built on a
per-host resource other than "slots" (e.g. a future absolute global mem
cap) needs ctx->alloc_req.host to carry that resource's job-wide total
want during the global phase, but only "slots" ever got that treatment
(via seqjob/parjob_prepare_allocation()'s own unconditional store).

Adds calc_wanted_host_resval_job_totals() (resreq.c), sharing its loop
body with calc_wanted_global_resvals() via a new static helper
parameterized only by which XCE_RESF_GLOBAL direction to match -- it
computes the SAME job-wide-total formulas (PER_TASK: value*nslots, PER_JOB:
value, PER_HOST: value*nhosts) for non-global resources instead of global
ones. seqjob/parjob_prepare_allocation()'s global-phase branch now calls
it into ctx->alloc_req.host alongside the existing calc_wanted_global_
resvals() call into .shared.

Safety was traced, not assumed: plugin_prepare_allocation() only resets
.host at the top of a per-host call, never during the global phase, and
sched_fill_limit_requests() for glimits reads .host later in the SAME
global-phase invocation -- transferring the value into the limit's
permanent .shared record before any later per-host call ever resets
.host. An earlier candidate fix (reusing calc_wanted_host_resvals()
directly) was rejected during design: its PER_HOST formula and, for
parjob, its per-bucket nslots don't give a job-wide total.

New regression tests in test_seqjob_allocator.c/test_parjob_
combinatorial.c prove a non-"slots" per-host resource ("mem") now gets
correctly populated; parjob's test uses maxTasks=3 specifically to prove
the formula uses the job's whole nslots, not a bucket's share.

Full suite (xce-build.sh all asan --incremental): 92/94, both failures
pre-existing and unrelated (bug-1762, bug-1733's already-documented
xcealloc.c leak). Not live-verified -- no limits.yaml entry exercises
this path yet.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GLfB5uWRdmx2WiZSFC7Fm7

src/include/resreq.h

@@ -315,6 +315,8 @@ extern int  calc_wanted_global_resvals(xvec_idval_t*, var, xlist_t*,
                                        rusage_per_type_t, int, int);
 extern int  calc_wanted_host_resvals(xvec_idval_t*, var, xlist_t*,
                                      rusage_per_type_t, int, int);
+extern int  calc_wanted_host_resval_job_totals(xvec_idval_t*, var, xlist_t*,
+                                               rusage_per_type_t, int, int);
 
 /*
  * Overwrite minTasks/maxTasks on resreq's own top-level primary with the