fix(admin-config-tool): resolve xceadmin config build warnings

Cross-reference warnings ("references undefined entry") were genuine
gaps in the example configs, not validator bugs: src/configs/hosts.yaml
had a typo'd resource ref (mg -> mem) and referenced a nonexistent
host3/hostgroup pair; queues.yaml referenced hgroup1/hgroup2/ugroup1
instead of the real hg1/ug1 names; resources.yaml was missing the
r1m/r15s/tmp built-in worker load-index resources
(worker/src/resource_sync.c's init_builtin_load_indices()). Added the
missing host3 host, hg2 hostgroup, ug2 usergroup, and three resource
entries; fixed the typo'd refs.

"schema-valid but has no ClusterConfig destination" warnings for
resources.yaml's type/order/consumable/release fields were a real gap
in xcecommon/mapping.py's _build_resource, not an inherent limitation
-- the encoding (XCE_VAL_*/xce_order_t/XCE_RESF_CONSUMABLE/
XCE_RESF_RELEASE) is documented in include/xce/types.h and actively
read by the scheduler; the old docstring's claim that it was
undocumented was wrong. Only resourcemap remains genuinely unmapped
(its capnp destination fields are commented out).

Updated test_mapping.py/test_config_build.py for the new mapping
behavior and regenerated the full golden fixture's expected.bin
(legitimate representation-drift from the mapping fix, not a bug).

src/configs/hosts.yaml

@@ -6,7 +6,7 @@ hosts:
     max_slot: -1
     description: "default host"
     resource:
-      - name: mg
+      - name: mem
       - name: maxswap
         value: 10000
     sched_stop:
@@ -30,10 +30,20 @@ hosts:
       - name: gstring
         value: "This is a G string"
 
+  - hostname: host3
+    type: "x86_64-linux-gnu"
+    model: "x86_64-linux-gnu"
+    max_slot: 128
+
 
 hostgroups:
   - groupname: hg1
     members:
       - all
-    exclude_members: [h3]
-    
+    exclude_members: [host3]
+
+  - groupname: hg2
+    members:
+      - worker2
+      - host3
+