[BulkActions] Consolidate se23 logic and styles (#10008)

Fixes #9921

Consolidates se23 beta styles for `BulkActions`.

Compare the bulk actions shadow bevel (make sure they are the same):

* This PR's
[Storybook](https://5d559397bae39100201eedc1-vxezcfotko.chromatic.com/?path=/story/all-components-indextable--default)
* [Production
Storybook](https://storybook.polaris.shopify.com/?path=/story/all-components-indextable--default&globals=polarisSummerEditions2023:true)

polaris-react/src/components/BulkActions/BulkActions.scss

@@ -61,7 +61,7 @@ $bulk-actions-button-stacking-order: (
 
   @include shadow-bevel(
     $boxShadow: var(--p-shadow-md),
-    $borderRadius: var(--p-border-radius-3)
+    $borderRadius: var(--p-border-radius-2)
   );
 
   @media #{$p-breakpoints-sm-down} {