(core) Improve highlighting of previewed formula

Summary:
Also improves highlighting of columns when the "Click to insert"
tooltip is shown, and improves highlighting of transforming columns.

Test Plan: Manual.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D3962

app/client/components/GridView.js

@@ -1139,7 +1139,8 @@ GridView.prototype.buildDom = function() {
                   },
                   menu(ctl => this.columnContextMenu(ctl, this.getSelection(), field, filterTriggerCtl)),
                   testId('column-menu-trigger'),
-                )
+                ),
+                dom('div.selection'),
               );
             }),
             this.isPreview ? null : kd.maybe(() => !this.gristDoc.isReadonlyKo(), () => (
@@ -1346,7 +1347,7 @@ GridView.prototype.buildDom = function() {
 
             kd.toggleClass('selected', isSelected),
             fieldBuilder.buildDomWithCursor(row, isCellActive, isCellSelected),
-            dom('div.field_selection')
+            dom('div.selection'),
           );
         })
       )