hosts: Add mtrcs0.p.r

*mtrcs0.pyrocufflink.red* is a Raspberry Pi CM4 on a Waveshare
CM4-IO-BASE-B carrier board with a NVMe SSD.  It runs a custom OS built
using Buildroot, and is not a member of the *pyrocufflink.blue* AD
domain.

*mtrcs0.p.r* hosts Victoria Metrics/`vmagent`, `vmalert`, AlertManager,
and Grafana.  I've created a unique group and playbook for it,
*metricspi*, to manage all these applications together.

group_vars/metricspi/grafana.yml

@@ -0,0 +1,18 @@
+grafana_allow_anonymous: true
+grafana_allow_sign_up: false
+grafana_allow_org_create: false
+grafana_ldap: true
+grafana_ldap_allow_sign_up: true
+grafana_ldap_host: dc2.pyrocufflink.blue
+grafana_ldap_use_ssl: true
+grafana_ldap_root_ca_cert: /etc/ssl/certs/dch-root-ca.crt
+grafana_ldap_bind_dn: CN=svc.grafana,CN=Users,DC=pyrocufflink,DC=blue
+grafana_ldap_bind_password: '{{ vault_grafana_ldap_bind_password }}'
+grafana_ldap_search_filter: '(sAMAccountName=%s)'
+grafana_ldap_base_dn: DC=pyrocufflink,DC=blue
+grafana_ldap_group_mapping:
+- group_dn: CN=Grafana Admins,CN=Users,DC=pyrocufflinke,DC=blue
+  role: Admin
+  grafana_admin: true
+- group_dn: '*'
+  role: Viewer