(core) Making cells colors effective also in Card and Card List views

Summary:
 . Makes cell color work well in comparison mode
 . Do not apply cell color to the add new row
 . Allow to change color for all widget (including changing color for the checkbox and the switch widget)
 . Fix an issue that was setting color to black when opening the picker
 . Do not apply color to invalid cell

Test Plan: . Added nbrowser/CellColor

Reviewers: paulfitz, dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2720

app/client/widgets/HyperLinkTextBox.ts

@@ -28,7 +28,7 @@ export class HyperLinkTextBox extends NTextBox {
           // from running on the same process as Grist:
           // https://developers.google.com/web/tools/lighthouse/audits/noopener
           dom.attr('rel', 'noopener noreferrer'),
-          cssLinkIcon('FieldLink'),
+          cssLinkIcon('FieldLink', testId('tb-link-icon')),
           testId('tb-link')
         )
       ),
@@ -62,10 +62,10 @@ function _constructUrl(value: string): string {
 }
 
 const cssFieldClip = styled('div.field_clip', `
-  color: ${colors.lightGreen};
+  color: var(--grist-actual-cell-color, ${colors.lightGreen});
 `);
 
 const cssLinkIcon = styled(icon, `
-  background-color: ${colors.lightGreen};
+  background-color: var(--grist-actual-cell-color, ${colors.lightGreen});
   margin: -1px 2px 2px 0;
 `);