Update owned entity guidance to explicitly call out that they don't work like value objects

**Guide**: https://docs.microsoft.com/en-us/dotnet/architecture/microservices/microservice-ddd-cqrs-patterns/implement-value-objects#persist-value-objects-as-owned-entity-types-in-ef-core-20

There is information relating to Owned Entities in EF Core included in this Value Object guide that does not exist on the Owned Entities document. Largely the `Persist value objects as owned entity types in EF Core 2.0` section.

Similarly shouldn't this document point out the relation to DDD Value Objects with a link to the guide or maybe even merging them?

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#### Document Details

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* ID: d02e6748-42e0-000a-4945-42cd05a0b875
* Version Independent ID: e3effbd0-07f2-423d-4032-1722e75adb37
* Content: [Owned Entity Types - EF Core](https://docs.microsoft.com/en-us/ef/core/modeling/owned-entities#feedback)
* Content Source: [entity-framework/core/modeling/owned-entities.md](https://github.com/aspnet/EntityFramework.Docs/blob/master/entity-framework/core/modeling/owned-entities.md)
* Product: **entity-framework**
* Technology: **entity-framework-core**
* GitHub Login: @AndriySvyryd
* Microsoft Alias: **ansvyryd**