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/resources.yaml

@@ -15,6 +15,29 @@ resources:
     order: decrease
     description: "available memory in MB (built-in dynamic load index)"
 
+    # built-in: worker load indices registered by
+    # worker/src/resource_sync.c init_builtin_load_indices()
+  - name: r1m
+    type: numeric
+    interval: 60
+    consumable: false
+    order: decrease
+    description: "1-minute load average (built-in dynamic load index)"
+
+  - name: r15s
+    type: numeric
+    interval: 60
+    consumable: false
+    order: decrease
+    description: "15-second load average (built-in dynamic load index)"
+
+  - name: tmp
+    type: numeric
+    interval: 60
+    consumable: false
+    order: decrease
+    description: "available tmp disk space in MB (built-in dynamic load index)"
+
     # built-in host attributes, registered per-worker by
     # controller/worker.c add_hostattrs_resvals()
   - name: type