FIX: supports groups field in post_created_edited (#28773)

To achieve this this commit does the following:
- create a new `groups field, ideally we would have reused the existing group field, but many automations now have the expectation that this field will return a group id and not an array of group ids, which makes it a dangerous change
- alter the code in `post_created_edited` to use this new groups field and change the logic to use an array
- migrate the existing group fields post_created_edited automations to change name from `restricted_group` to `restricted_groups`, the component from `group` to `groups` and the metadata from `{"value": integer}` to `{"value": [integer]}`

plugins/automation/app/models/discourse_automation/field.rb

@@ -188,6 +188,12 @@ module DiscourseAutomation
           "type" => "integer",
         },
       },
+      "groups" => {
+        "value" => {
+          "type" => "array",
+          "items" => [{ type: "integer" }],
+        },
+      },
       "email_group_user" => {
         "value" => {
           "type" => "array",