[Blazor] Type inference improvement: RenderFragment parameters

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

Consider 3 Blazor components: `MyWidgetsPage`, `WidgetsDisplay`, and `DataGrid`. `DataGrid` is marked with `[CascadingTypeParameter(nameof(TGridItem))]`.

`WidgetsDisplay` contains an instance of `DataGrid`. Any children of that component, such as a `TemplateColumn`, will be automatically passed the type argument `Widget`. `WidgetsDisplay` also has a `[Parameter] RenderFragment` called `ExtraColumns` that is used inside the data grid.

`MyWidgetsPage` has a `WidgetsDisplay`. In the `ExtraColumns` argument, there are some more `TemplateColumn`s. Theoretically, the Blazor compiler should be able to infer the type argument `Widget`, but it currently has no way of knowing that `ExtraColumns` is only used in a context where it's given a cascading type parameter. So, I have to manually specify `T="Widget"` in each child component. Not a huge problem, but still an area where Blazor could improve.

### Describe the solution you'd like

I would love to be able to specify on a RenderFragment parameter what type variables it has access to. Something like:

```cs
[CascadingType(nameof(DataGrid.TGridItem), nameof(Widget)), Parameter] public RenderFragment ExtraColumns { get; set; }
```

Current workarounds include just specifying the type parameters explicitly (as in the code below), or making the whole `WidgetDisplay` component generic with a type constraint to `Widget`.

### Additional context

Example code from the problem statement:

`DataGrid.razor`
```razor
@typeparam TGridItem
@attribute [CascadingTypeParameter(nameof(TGridItem))]

@code {
[Parameter] public IEnumerable Items { get; set; }
[Parameter] public RenderFragment ChildContent { get; set; }
}
```

`WidgetsDisplay.razor`
```razor

@ExtraColumns

Do Something

@code {
[Parameter] public IEnumerable Widgets { get; set; }
[Parameter] public RenderFragment ExtraColumns { get; set; }
}
```

`MyWidgetsPage.razor`
```razor

@context.GetBar()

```

Start with the DataGrid.razor, WidgetsDisplay.razor, and MyWidgetsPage.razor examples to reproduce the missing type inference. Then trace the Blazor compiler handling for RenderFragment parameters and cascading type parameters. Done means a RenderFragment declaration can expose the relevant type variable so nested TemplateColumn components infer Widget without explicit TGridItem arguments.

Written by the indexing model from the issue text.