Update mixin dashboard

Update and rewrite the mixin dashboards to use the grafonnet ([1])
library.
Grafana has deprecated angular plugins ([2]) as used by grafonnet-lib
([3]) with removal pending for grafana version 12.
Additionally grafonnet-lib is deprecated/unmaintained in favor of
grafonnet.
Therefore the mixin dashboards have been updated to use grafonnet.

Closes: https://github.com/prometheus/prometheus/issues/14404

[1]
https://github.com/grafana/grafonnet

[2]
https://grafana.com/docs/grafana/latest/developers/angular_deprecation/

[3]
https://github.com/grafana/grafonnet-lib

Signed-off-by: Jan Horstmann <horstmann@osism.tech>

documentation/prometheus-mixin/jsonnetfile.json

@@ -4,20 +4,11 @@
     {
       "source": {
         "git": {
-          "remote": "https://github.com/grafana/grafonnet-lib.git",
-          "subdir": "grafonnet"
+          "remote": "https://github.com/grafana/grafonnet.git",
+          "subdir": "gen/grafonnet-latest"
         }
       },
-      "version": "master"
-    },
-    {
-      "source": {
-        "git": {
-          "remote": "https://github.com/grafana/jsonnet-libs.git",
-          "subdir": "grafana-builder"
-        }
-      },
-      "version": "master"
+      "version": "main"
     }
   ],
   "legacyImports": false