Add advantages and disadvantages of each loading method

It would be helpful to know the drawbacks of each loading method. For example, lazy loading requires less code (i.e. no `Include` calls needed) but results in sending more queries when compared to loading things with just 1 query with `Include` and `ThenInclude`. It would help to decide which method to use.

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#### Document Details

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* ID: bbd36f35-e257-d0ed-8f28-f539ddcb71ec
* Version Independent ID: 093903d5-f7c7-5a78-c0e5-0e2662dcedef
* Content: [Loading Related Data - EF Core](https://docs.microsoft.com/en-us/ef/core/querying/related-data)
* Content Source: [entity-framework/core/querying/related-data.md](https://github.com/aspnet/EntityFramework.Docs/blob/master/entity-framework/core/querying/related-data.md)
* Product: **entity-framework**
* GitHub Login: @rowanmiller
* Microsoft Alias: **divega**