[In-Proc] Split `Microsoft.Azure.WebJobs.Script.WebHost.InProc` package reference by target framework

The `in-proc` branch of Core Tools multi-targets `net6.0` and `net8.0`, but uses a **single, shared** `Microsoft.Azure.WebJobs.Script.WebHost.InProc` package reference for both target frameworks:

```xml

```

This means that any update to the in-proc host package requires a new Core Tools build that ships **both** .NET 6 and .NET 8 bits simultaneously. There is no way to service .NET 8 independently of .NET 6 (or vice-versa).

### Considerations

- We will need to update the nuget reference
- We will need to update `validateWorkerVersions.ps1`
- CI/CD pipelines — Review for any automation that assumes a single InProc host version (e.g., automated version bumps).

Start with the in-proc branch project file containing the Microsoft.Azure.WebJobs.Script.WebHost.InProc package reference, then inspect validateWorkerVersions.ps1 and CI/CD automation for assumptions about one host version. Done means the net6.0 and net8.0 references can be serviced independently and validation and version-bump automation handle the split.

Written by the indexing model from the issue text.