Add BackgroundImage to Tabbar

### Description

I know it has the background property but it only works with colors, sometimes you need to place an image, but also since there is a TitleView it wouldn't be bad to have a TabBarView that allows you to create a more attractive TabBar.

### Public API Changes

.

### Intended Use-Case

.

Start by reviewing the existing TabBar background property and the TitleView API in the .NET MAUI codebase. Clarify whether the request is for image backgrounds, a new TabBarView, or both, then define the affected platforms and acceptance criteria before identifying implementation and test locations.

Written by the indexing model from the issue text.