Fix columns full-wide regression. (#18021)

The Columns block, when full-wide, has intentional left and right padding to ensure the mover controls of child blocks are accessible. This is editor-only, and only when the block is selected.

This regressed at some point, a while ago, probably around the introduction of extra on-click padding to show the dashed outlines of child elements.

This PR shuffles the rules a bit, reduces some of their specificity, and applies the left and right padding elsewhere to make it work.

packages/block-library/src/columns/editor.scss

@@ -12,18 +12,6 @@
 	}
 }
 
-// Fullwide: show margin left/right to ensure there's room for the side UI.
-// This is not a 1:1 preview with the front-end where these margins would presumably be zero.
-[data-type="core/columns"][data-align="full"] .wp-block-columns > .editor-inner-blocks {
-	padding-left: $block-padding;
-	padding-right: $block-padding;
-
-	@include break-small() {
-		padding-left: $block-container-side-padding;
-		padding-right: $block-container-side-padding;
-	}
-}
-
 .wp-block-columns {
 	display: block;
 
@@ -188,10 +176,10 @@ div.block-core-columns.is-vertically-aligned-bottom {
 /**
  * Add extra padding when the parent block is selected, for easier interaction.
  */
-.block-editor-block-list__layout .block-editor-block-list__block[data-type="core/columns"].is-selected > .block-editor-block-list__block-edit > [data-block] > div > .block-editor-inner-blocks,
-.block-editor-block-list__layout .block-editor-block-list__block[data-type="core/columns"].has-child-selected > .block-editor-block-list__block-edit > [data-block] > div > .block-editor-inner-blocks,
-.block-editor-block-list__layout .block-editor-block-list__block[data-type="core/column"].is-selected > .block-editor-block-list__block-edit > [data-block] > div > .block-editor-inner-blocks,
-.block-editor-block-list__layout .block-editor-block-list__block[data-type="core/column"].has-child-selected > .block-editor-block-list__block-edit > [data-block] > div > .block-editor-inner-blocks {
+[data-type="core/columns"].is-selected > .block-editor-block-list__block-edit > [data-block] > div > .block-editor-inner-blocks,
+[data-type="core/columns"].has-child-selected > .block-editor-block-list__block-edit > [data-block] > div > .block-editor-inner-blocks,
+[data-type="core/column"].is-selected > .block-editor-block-list__block-edit > [data-block] > div > .block-editor-inner-blocks,
+[data-type="core/column"].has-child-selected > .block-editor-block-list__block-edit > [data-block] > div > .block-editor-inner-blocks {
 	padding: $block-padding;
 
 	// Negate this padding for the placeholder.
@@ -200,3 +188,16 @@ div.block-core-columns.is-vertically-aligned-bottom {
 		width: calc(100% + #{$block-padding * 2});
 	}
 }
+
+
+// Fullwide: show margin left/right to ensure there's room for the side UI.
+// This is not a 1:1 preview with the front-end where these margins would presumably be zero.
+[data-type="core/columns"][data-align="full"] .wp-block-columns {
+	padding-left: $block-padding;
+	padding-right: $block-padding;
+
+	@include break-small() {
+		padding-left: $block-container-side-padding;
+		padding-right: $block-container-side-padding;
+	}
+}