(core) Fixing cursor position for filtered linked section.

Summary:
In a selector table, when a selected row is filtered out of view, linked widgets should update based on the newly selected row.
There were a few bugs that contributed to this wrong behavior:
- Gridview wasn't subscribing to the current row id, and the row with id 'new' was being converted to the first row
- Cursor was keeping track of the currently selected row id, it was hiding a problem behind the proper rowIndex
- Undo/redo somehow leveraged the wrong rowId from the cursor during the position restore.

The `No data` text was also changed to be more meaningful.

Test Plan: Added and updated.

Reviewers: georgegevoian

Reviewed By: georgegevoian

Differential Revision: https://phab.getgrist.com/D3937

app/client/lib/sortUtil.ts

@@ -5,6 +5,7 @@ import * as rowset from 'app/client/models/rowset';
 import { MANUALSORT } from 'app/common/gristTypes';
 import { SortFunc } from 'app/common/SortFunc';
 import { Sort } from 'app/common/SortSpec';
+import { UIRowId } from 'app/common/TableData';
 import * as ko from 'knockout';
 import range = require('lodash/range');
 
@@ -44,7 +45,7 @@ export async function updatePositions(gristDoc: GristDoc, section: ViewSectionRe
   sortFunc.updateSpec(section.activeDisplaySortSpec.peek());
   const sortedRows = rowset.SortedRowSet.create(
     null,
-    (a: rowset.RowId, b: rowset.RowId) => sortFunc.compare(a as number, b as number),
+    (a: UIRowId, b: UIRowId) => sortFunc.compare(a as number, b as number),
     tableModel.tableData
   );
   sortedRows.subscribeTo(tableModel);