Rewrite using Brighter HostBuilder support

[iancooper]

The project uses an older approach to explicit initialization, that is long-winded and confusing to users. instead, it should use the new HostBuilder support that Brighter has to make this simple and clean.

Alongside this, we can drop the use of SimpleInjector in favour of vanilla ServiceCollection - we don't really use any features of SimpleInjector here.

Finally, this project has slid behind on versions, and should bu updated