Fixer/Analyzer: Hoist explicit calls to HttpContext.RequestServices.GetService to route handler parameters

We should have a fixer that rewrites calls to GetRequiredService to injecting them directly into handler methods. Code should go from this:

```C#
app.MapGet("/", (HttpContext context) =>
{
var service = context.RequestServices.GetRequiredService();
return service.GetTodos();
});
```

To this:

```C#
app.MapGet("/", (ITodoService service) =>
{
return service.GetTodos();
});
```

No files or tests are named. Start by locating the analyzer and fixer entry points for MapGet route handlers, then use the GetRequiredService example as the reproduction. Done means the explicit service lookup is represented as a handler parameter and existing analyzer/fixer tests cover the transformation.

Written by the indexing model from the issue text.