RowDefinition's and ColumnDefinition's IsVisible

### Description

Hi,

Many times we need to show or hide a Row in the codebehind so it will be much easier to add IsVisible property to the RowDefination and ColumnDefination to show the specific row or column.

### Public API Changes

```
myRow.IsVisible = false
myColumn.IsVisible = false;

```

### Intended Use-Case

Where we have a lot of rows or columns and need to hide the row / column in an easy ay instead if using Twiggers or any other workaround

The issue names no files, tests, or entry points. Start by locating RowDefinition and ColumnDefinition and reviewing how their layout participation is calculated, then check existing layout tests. Done means both definitions expose the requested IsVisible behavior and verified tests show rows and columns can be hidden and shown.

Written by the indexing model from the issue text.