(core) Implement 'Print widget' option to print individual view sections.

Summary:
- Supports multi-page printing with some aggressive css overrides.
- Relies on a new function implemented by grist-plugin-api to print a
  multi-page CustomView.
- Renders all rows for printing for scrolly-based views.

Test Plan:
Doesn't seem possible to do a selenium test for printing. Tested
manually on Chrome, Firefox, and Safari.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2635

app/client/ui/PagePanels.ts

@@ -199,6 +199,12 @@ const cssTopHeader = styled('div', `
 const cssResizeFlexVHandle = styled(resizeFlexVHandle, `
   --resize-handle-color: ${colors.mediumGrey};
   --resize-handle-highlight: ${colors.lightGreen};
+
+  @media print {
+    & {
+      display: none;
+    }
+  }
 `);
 const cssResizeDisabledBorder = styled('div', `
   flex: none;

app/client/ui/ViewLayoutMenu.ts

@@ -9,17 +9,19 @@ import {dom} from 'grainjs';
  */
 export function makeViewLayoutMenu(viewModel: ViewRec, viewSection: ViewSectionRec, isReadonly: boolean) {
   return [
+    menuItemCmd(allCommands.printSection, 'Print widget', testId('print-section')),
     dom.maybe((use) => ['detail', 'single'].includes(use(viewSection.parentKey)), () =>
       menuItemCmd(allCommands.editLayout, 'Edit Card Layout',
         dom.cls('disabled', isReadonly))),
 
+    menuDivider(),
+    menuItemCmd(allCommands.viewTabOpen, 'Widget options', testId('widget-options')),
+    menuItemCmd(allCommands.sortFilterTabOpen, 'Advanced Sort & Filter'),
+    menuItemCmd(allCommands.dataSelectionTabOpen, 'Data selection'),
+
+    menuDivider(),
     menuItemCmd(allCommands.deleteSection, 'Delete widget',
       dom.cls('disabled', viewModel.viewSections().peekLength <= 1 || isReadonly),
       testId('section-delete')),
-    menuDivider(),
-
-    menuItemCmd(allCommands.viewTabOpen, 'Widget options', testId('widget-options')),
-    menuItemCmd(allCommands.sortFilterTabOpen, 'Advanced Sort & Filter'),
-    menuItemCmd(allCommands.dataSelectionTabOpen, 'Data selection')
   ];
 }