[http-server-csharp] Allow user to choose how arrays are treated.

### Clear and concise description of the problem

Right now properties that are collections are emitted as Array. But integration with other systems like Entity Framework require ICollection or other collection type.
https://learn.microsoft.com/en-us/ef/core/modeling/relationships/navigations#collection-types

It would be nice if the user could specify how they would like their arrays to be emitted. This includes the model properties and the operation iterfaces.

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/microsoft/typespec/blob/main/CODE_OF_CONDUCT.md)
- [x] Read the [docs](https://typespec.io/docs/).
- [x] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.