DEV: Refactor the Automation Plugin UI to match admin UI guidelines (#31060)

This change updates the Automation plugin to make use of the `use_new_show_route` plugin flag, as well as generally updating the UI to match current admin UI guidelines. Notable changes include:

- Moving template/router/controller files to make use of the `admin.adminPlugins.show` route.
- Changing the URIs from `/admin/plugins/discourse-automation` to `/admin/plugins/automation`, to match the `PLUGIN_NAME`.
- Adding UI wrappers around the New/Edit forms, and polishing the list of defined automations.

plugins/automation/assets/stylesheets/common/discourse-automation.scss

@@ -1,4 +1,4 @@
-.discourse-automation {
+.admin-plugins.automation {
   .automations {
     .relative-date {
       font-size: $font-down-1;
@@ -13,6 +13,10 @@
     }
   }
 
+  .discourse-automations-table {
+    margin-top: 1em;
+  }
+
   .d-admin-table.automations {
     .d-admin-row__content {
       @include breakpoint("tablet") {
@@ -51,6 +55,18 @@
         order: 5;
       }
     }
+
+    .d-admin-row__controls.automations__controls {
+      text-align: right;
+      display: flex;
+      flex-direction: row;
+      gap: 0.5em;
+      justify-content: flex-end;
+
+      @include breakpoint("tablet") {
+        order: 6;
+      }
+    }
   }
 
   .admin-section-landing__header {