Adding support for custom JsonConverter(s) when deserializing JSON Patch value object

[onegoodsausage]

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PR Title
Adding support for custom JsonConverter(s) when deserializing JSON Patch value object

PR Description
When we started using the JSON Patch library we hit an issue with heterogenous collections. To specify what type an object in a heterogenous collection is, we added a "Type" property to the JSON value object. However, regardless of what we supplied in our custom ContractResolver, nothing was getting used when the JObject was converted to a concrete object.

Once we looked at the sources we found out that the JsonPatchDocument.ContractResolver is not used at all when deserializing the value object. So we added an overload that takes an IContractResolver and wired it up for the ListAdapter.

That solved our issue as now our custom JsonConverter is used to read the "Type" property and create the correct object instance. We also added an integration unit test that covers this scenario.

[dnfadmin]

All CLA requirements met.

[ghost]

Thank you for submitting this for API review. This will be reviewed by @dotnet/aspnet-api-review at the next meeting of the ASP.NET Core API Review group. Please ensure you take a look at the API review process documentation and ensure that:

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[pranavkm]

How do you feel about this? It avoids an additional public API