GetEndpointAttribute<T> in EndpointHttpContextExtensions.cs

### Is your feature request related to a problem?
Not a problem, just a nice-to-have. It'd be convenient to be able to fetch route attributes directly from `HttpContext`. I've found it comes up pretty often when working with custom middleware, it's not a long path to get to the metadata from the context itself as it is now, but as there's already extensions to fetch the endpoint itself from `HttpContext`, it may also be useful to include something like this and maybe another extension to fetch a collection of route attributes.

### Describe the solution you'd like
Perhaps something like `GetEndpointAttribute` and `GetEndpointAttributes` in `EndpointHttpContextExtensions.cs` alongside the other endpoint-related extensions.

### Additional context
This is the basic idea (minus handling nulls, etc - that'd be handled the same way it is right now in `GetEndpoint`)

```csharp
public static T GetEndpointAttribute(this HttpContext httpContext) where T : Attribute
{
var attribute = httpContext
.Features
.Get()
.Endpoint
.Metadata.GetMetadata();

return attribute;
}
```