Ben Bryant

I tried updating to .NET 8 and fixed what was broken. Very little needed to be fixed to get it working, but a bunch of new warnings showed up so...

This enables [nullable reference types](https://learn.microsoft.com/en-us/dotnet/csharp/nullable-references) for the 3 core projects (Infrastructure.Framework, Domain, Extensions). I tried enabling it solution-wide but that resulted in another >300 warnings that I didn't want to...

[PM-22470] Enable NRT for more Core project files

4

## 🎟️ Tracking Related to [this ADR](https://contributing.bitwarden.com/architecture/adr/csharp-nullable-reference-types/), but until that's accepted I'm working in the other direction and enabling per-file instead (as discussed [here](https://github.com/orgs/bitwarden/discussions/15033)). ## 📔 Objective  This PR...