[Feature]: Rename elasticstack_full_stack to reflect its residual meaning (inventory wiring) #535

After the other meanings are peeled off (see #531), elasticstack_full_stack has one remaining job: inventory-based host wiring — the roles resolving Elasticsearch and each other from inventory groups (vs a standalone single role pointing at user-provided targets). The name no longer reflects that, so rename it — without a backward-compat alias (clean break, 2.0.0).

Proposed name (TBD — pick one):

• elasticstack_integrated — components are wired together, vs standalone. Short.
• elasticstack_collection_managed_stack — "the collection manages the whole stack". Intuitive but broad.
• elasticstack_wire_from_inventory — most literal (resolve peers from inventory groups). A bit technical.
• elasticstack_inventory_managed — topology managed via inventory groups.

Do this last, after (A)/(C)/(D) are removed. Breaking → 2.0.0. Part of #531.