Dashboard Conversion: Preserve repeat property when converting tabs to rows (#116180)

* preserve repeat property

* fix test

* preserve repeat when converting panels in tabs or rows with autogrid layout

* fix v1 serialization of autogrid

apps/dashboard/pkg/migration/conversion/testdata/output/v2beta1.tabs-and-rows-repeated.v0alpha1.json

@@ -586,6 +586,7 @@
         },
         "id": -1,
         "panels": [],
+        "repeat": "custom_var_tab",
         "title": "Repeated Tab by \"$custom_var_tab\"",
         "type": "row"
       },
@@ -610,8 +611,11 @@
           "y": 22
         },
         "id": 6,
+        "maxPerRow": 3,
         "options": {},
         "pluginVersion": "12.4.0-19736337744",
+        "repeat": "custom_var_panel",
+        "repeatDirection": "h",
         "targets": [
           {
             "refId": "A"

apps/dashboard/pkg/migration/conversion/testdata/output/v2beta1.tabs-and-rows-repeated.v1beta1.json

@@ -586,6 +586,7 @@
         },
         "id": -1,
         "panels": [],
+        "repeat": "custom_var_tab",
         "title": "Repeated Tab by \"$custom_var_tab\"",
         "type": "row"
       },
@@ -610,8 +611,11 @@
           "y": 22
         },
         "id": 6,
+        "maxPerRow": 3,
         "options": {},
         "pluginVersion": "12.4.0-19736337744",
+        "repeat": "custom_var_panel",
+        "repeatDirection": "h",
         "targets": [
           {
             "refId": "A"