[two_dimensional_scrollables] Post 3.16 stable tech debt clean up (flutter#5671)

Fixes flutter#136933
Fixes flutter#132782

This cleans up some TODOs in the TableView and its tests after the stable release
- removes an assertion on the builder delegate bounds now that the super class handles the assertions
- refactors all of the golden file tests using PaintPattern, removing all of the golden files and enabling web testing

Author: Piinks

packages/two_dimensional_scrollables/dart_test.yaml

@@ -150,8 +150,6 @@ class TableCellBuilderDelegate extends TwoDimensionalChildBuilderDelegate
   int get columnCount => maxXIndex! + 1;
   set columnCount(int value) {
     assert(pinnedColumnCount <= value);
-    // TODO(Piinks): remove once this assertion is added in the super class
-    assert(value >= -1);
     maxXIndex = value - 1;
   }
 
@@ -180,8 +178,6 @@ class TableCellBuilderDelegate extends TwoDimensionalChildBuilderDelegate
   int get rowCount => maxYIndex! + 1;
   set rowCount(int value) {
     assert(pinnedRowCount <= value);
-    // TODO(Piinks): remove once this assertion is added in the super class
-    assert(value >= -1);
     maxYIndex = value - 1;
   }