Distinct does not work on Enumerable<IEdmStructuredType>

https://github.com/microsoft/OpenAPI.NET.OData/blame/c00a26b629e76d624f80911d4b97d9ae86af9cf7/src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiSchemaGenerator.cs#L197 produces duplicates, when there is a navigation property to an entity that is already associate in the entity sets. In our case the EntityType is not the same instance, so it MUST be compared by FullName to get distinct values. I made the same mistake recently, so it would be nice if there is a default comparer.

打开 src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiSchemaGenerator.cs 的第 197 行，检查 Enumerable 值是如何去重的。复现 issue 中描述的重复 entity-set 情况，并按 FullName 而不是实例标识比较实体。完成的标准是 navigation properties 不再产生重复值，并且现有测试套件通过。