tests: bluetooth: shell: Add test case to build shell with plm

Path loss monitoring was not being enabled anywhere, meaning
that issues could be merged in without catching the issue.

This commit adds a test case to build the shell with path
loss monitoring enabled to catch issues.

Signed-off-by: Sean Madigan <sean.madigan@nordicsemi.no>

tests/bluetooth/shell/testcase.yaml

@@ -29,6 +29,13 @@ tests:
     platform_allow:
       - native_sim
     build_only: true
+  bluetooth.shell.path_loss_monitoring:
+    extra_configs:
+      - CONFIG_BT_PATH_LOSS_MONITORING=y
+      - CONFIG_BT_CTLR=n
+    platform_allow:
+      - native_posix
+    build_only: true
   bluetooth.shell.subrating:
     extra_configs:
       - CONFIG_BT_SUBRATING=y