refactor(menu): improve chromatic cov, prevent checkbox + icon clash(#2757)

- refactor menu item

- create single menu item story
- create menu with variants story
- build chromatic testing views for menu item and menu with variants
- remove extra stories in favor of using menu with variants

- fix to prevent multiselect checkbox and icon clash

CSS-614

Author: rise-erpelding

.changeset/silly-ties-attend.md

@@ -0,0 +1,7 @@
+---
+"@spectrum-css/menu": patch
+---
+
+Prevents overlap of checkbox and icon if both are used in a menu item.
+
+Also reduces a significant number of variants by consolidating menus, includes a refactor to enhance menu item understanding, and expands Chromatic testing coverage.

components/menu/index.css

@@ -513,7 +513,7 @@ governing permissions and limitations under the License.
 }
 
 .is-selectableMultiple .spectrum-Menu-itemCheckbox {
-	grid-area: iconArea;
+	grid-area: checkmarkArea;
 }
 
 .spectrum-Menu-checkmark {