.NET 7 MAUI CollectionView doesn't support the UIA Grid pattern

### Description

Run the demo app listed in the Repro steps, and point Accessibility Insights for Windows to the running CollectionView. Accessibility Insights shows that the CollectionView doesn't support the UIA Grid pattern, and the CollectionView's items don't support the UIA GridItem pattern. This means the Narrator screen reader can't announce the row and column of an item as the user moves through the items in the CollectionView.

### Steps to Reproduce

1. Run the app at https://github.com/gbarkerz/MauiAppTest2.
2. Point Accessibility Insights for Windows to the CollectionView.

Result: The CollectionView doesn't support the Grid pattern.
Expected: The CollectionView shows a grid of items which can be navigated through as a grid, so the grid should support the UIA Grid pattern.

### Link to public reproduction project repository

https://github.com/gbarkerz/MauiAppTest2

### Version with bug

7.0 (current)

### Last version that worked well

Unknown/Other

### Affected platforms

Windows

### Affected platform versions

net7.0-windows10.0.19041.0

### Did you find any workaround?

No.

### Relevant log output

_No response_

Start by running the demo app at https://github.com/gbarkerz/MauiAppTest2 on Windows and inspect its CollectionView with Accessibility Insights for Windows. Confirm the missing UIA Grid and GridItem patterns, then trace the Windows CollectionView accessibility implementation. Done means the CollectionView exposes the Grid pattern and its items expose GridItem information so Narrator can announce row and column positions.

Written by the indexing model from the issue text.