GOSS-Core: fix develop-tag startup activation-order race (GRIDAPPSD/GOSS-GridAPPS-D#1882) + follow-ups

[craigpnnl]

Tracking issue for the GOSS-Core activation-order fix that resolves the GridAPPS-D develop-tag startup failure reported in GRIDAPPSD/GOSS-GridAPPS-D#1882, plus the follow-up items surfaced during diagnosis and review.

Root cause

Declarative Services activation-order race introduced by the DependencyManager to DS migration (commit d687f17). GridOpticsServer.start() authenticates system/manager against the Shiro realm set before the system-authenticating realm is registered, so startup dies nondeterministically with "Realm UnauthTokenBasedRealm was unable to find account data for system". Machine and startup-path dependent.

Primary fix

Mandatory @Reference(target="(realm.type=system)") gates on the system realm binding (SecurityManager publication + GridOpticsServer activation), plus collapse of the double-writer race to a single realm-set writer in Activator. Reviewed: fail-closed confirmed, no fail-open window, no dropped realm.

Follow-ups (sub-issues)

Items found during diagnosis/review that are out of scope for the primary fix. See the linked sub-issues.

[craigpnnl]

All work tracked here is complete and merged to develop: the #1882 activation-order fix (PR #44), and the three follow-ups #41 (PR #45), #42 (PR #45), #43 (PR #47). Closing the tracking issue.