Support EFCore HierarchyId datatype

[adamskt]

Current behavior:

1. Create a new Coalesce project from the template
2. Add the Microsoft.EntityFrameworkCore.SqlServer.HierarchyId package to the project
3. Add a property to a model that uses the type HierarchyId
4. Code generation fails with:

** Failure: Coalesce.TestProject.Data.Models.MyModel,MyModelHierarchyId: The target object for the property has no discernible display text. Add a [ListTextAttribute] to one of its properties.

Currently this behavior can be worked around by decorating the new property with the [InternalUse] property, but then the property will be ignored by Coalesce and not show up in generated DTOs or Typescript types.

Tasks

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1. Add the Microsoft.EntityFrameworkCore.SqlServer.HierarchyId package to Coalesce
2. Add the above package to the generated solution
3. Add a check in the context validation to recognize usage of the HierarchyId type
4. Add a special case in DTO generators and mappers to convert HierarchyId to a string type and back
5. Add HierarchyId properties to test fixtures and expand tests to assert that APIs, DTOs and Typescript types generate properly for the new types