Easier way to read QueryProperty

### Description

Currently, we have to use a class to get and set the QueryProperty.

This can be reduced to one line only by introducing a new **GetQueryProperty** method.

### Public API Changes

```
namespace MyApp;

[QueryProperty("Organization", "MyOrganization")]
public partial class StartVote : ContentPage
{
string organization = GetQueryProperty("MyOrganization");

public StartVote()
{
InitializeComponent();
}
.............
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}

```

### Intended Use-Case

Make coding easier.

The issue names QueryProperty and proposes a new GetQueryProperty method, but it does not identify implementation files or tests. Start by locating QueryProperty handling and its navigation/property-application tests; done means the proposed one-line access pattern works without the existing helper class and is covered by tests.

Written by the indexing model from the issue text.