Site editor: bump the z-index of the rename modal (#54277)

* This commit bumps the rename modal z-index to be one higher than the dropdown popover component, which is set to 1000000 in the component stylesheet

* Update style.scss

The +1 is unnecessary thanks to document tree order.

* Add z-index entry

* Moving styles to existing stylesheet

packages/base-styles/_z-index.scss

@@ -126,6 +126,7 @@ $z-layers: (
 	".block-editor-block-lock-modal": 1000001,
 	".block-editor-template-part__selection-modal": 1000001,
 	".block-editor-block-rename-modal": 1000001,
+	".edit-site-list__rename-modal": 1000001,
 
 	// Note: The ConfirmDialog component's z-index is being set to 1000001 in packages/components/src/confirm-dialog/styles.ts
 	// because it uses emotion and not sass. We need it to render on top its parent popover.

packages/edit-site/src/components/list/style.scss

@@ -130,6 +130,8 @@
 }
 
 .edit-site-list__rename-modal {
+	// The rename dropdown popover is open at the same time as the rename modal. The latter has to be higher.
+	z-index: z-index(".edit-site-list__rename-modal");
 	.components-base-control {
 		@include break-medium() {
 			width: $grid-unit * 40;

packages/edit-site/src/components/page-patterns/rename-menu-item.js

@@ -79,7 +79,7 @@ export default function RenameMenuItem( { item, onClose } ) {
 						setIsModalOpen( false );
 						onClose();
 					} }
-					overlayClassName="edit-site-list__rename_modal"
+					overlayClassName="edit-site-list__rename-modal"
 				>
 					<form onSubmit={ onRename }>
 						<VStack spacing="5">