Engineering: introduce updated editorconfig

Part of #1655

We will settle on and introduce a new editorconfig which encourages using the latest C# language features where available.

See [.editorconfig](https://github.com/jviau/dotnet-worker-layout/blob/main/.editorconfig) for a starting point

## Requirements

- Modern style enforcement
- Enforced on build
- Enforced for source projects

## Non-Requirements

- Strict rules for sample and test projects

We will want to decide how to onboard projects gradually to the new editorconfig. The end goal is to have **all** source projects onboarded. We can also come up with a less-strict subset of rules for test and sample projects.