Task 1.1: new deep-copy for xce_job_alloc_t composed from existing
make_alloc/make_host_alloc/make_job_alloc, explicitly preserving each
allocation's original from/duration rather than accepting make_alloc's
own time(NULL) stamp. TDD: 6 new unit tests (single-host, multi-host,
multi-resource-per-host, shared-resource-pool, independence-after-free,
from/duration fidelity), all passing under ASAN.
Also logs bug-1723 (pre-existing, unrelated leak in two bug-1722 test
fixtures, confirmed via git-stash A/B rebuild to be byte-for-byte
identical before and after this change) -- documentation only, not fixed
here.
Requirements: 1.1, 1.4