`DbContextCheck` should work together with `IDbContextFactory`

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

We use the `services.AddDbContextCheck()` method to monitor the connection to the database in our apps. Due to performance reasons we switched to using `IDbContextFactory` to access instances of EF Core DbContext:

```csharp
services.AddPooledDbContextFactory(dbContextOptions)
```

When we did so, we noticed that the `DbContextHealthCheck` does not support the factory and, thus, we had to register the DbContext directly to keep the HealthCheck working:

```csharp
// This is just required for the HealthCheck, since it does not (yet?) work with the Factory.
services.AddDbContextPool(dbContextOptions);
```

### Describe the solution you'd like

The `DbContextHealthCheck` should support `IDbContextFactory` without any additional service registrations.

### Additional context

We are willing to invest some time to implement this and submit a pull request. But we need some support on how we should implement this and how the API should look like.