Adds apiserver_push_jobarray() (apiserver.c), mirroring task 5.1's
xcesched_push_jobarray() exactly: same (base jobid, array_size, one
spec) Data.jobArray derivation, same direct xce_request()/OPCode_push
transport. apiserver_job_new_fun() branches on l->count > 1; the
existing single-job path (apiserver_push_joblist()) is byte-for-byte
unchanged.
Additionally, and unlike the scheduler (single target), replicates
apiserver_push_joblist()'s existing per-connected-server fan-out loop
(N_APISERVER_MAX iteration, same lock discipline) -- verified against
2 simulated connected servers, each receiving exactly one push.
New standalone apiserver_push_unit_test binary (same link-collision
rationale as task 5.1's sched_push_unit_test), correctly omitting
egress.c since apiserver_push_joblist() has no WAL-commit filter.
Task 5.2 of job-array-single-wal-record (Requirements 6.2, 6.4).
Rongsong Shen
e0cec75284