Remove System.Text.Json reference in Microsoft.Toolkit.Uwp package

[michael-hawker]

Describe the bug

We're only using this dependency (which is large) for a single helper in the package. We should streamline this with some docs instead of having a hard dependency. This also makes it easier for folks to use either Newtonsoft.Json or System.Text.Json depending on what their app is already using.

Add docs for:

using System.Text.Json;

namespace Microsoft.Toolkit.Uwp.Helpers
{
    public class JsonObjectSerializer : IObjectSerializer
    {
        public string Serialize<T>(T value) => JsonSerializer.Serialize(value);

        public T Deserialize<T>(string value) => JsonSerializer.Deserialize<T>(value);
    }
}

using Newtonsoft.Json;

namespace Microsoft.Toolkit.Uwp.Helpers
{
    internal class JsonObjectSerializer : IObjectSerializer
    {
        public string Serialize<T>(T value) => JsonConvert.SerializeObject(value);

        public T Deserialize<T>(string value) => JsonConvert.DeserializeObject<T>(value);
    }
}

Instead of including explicitly. This will help with #3145 as most other higher-level toolkit libs are including the UI package which also includes this package.

FYI @vgromfeld @simop-msft

[michael-hawker]

Snafu... the SystemInformation helpers use the LocalObjectStorageHelper which uses this...

Instead of completely requiring the developer to specify the serialization option, do we want to provide a base implementation which uses DataContractJsonSerializer instead? This would basically complete the original #889 issue.

At least for the SystemInformation class, I believe that would be simple enough in terms of data structure to be able to directly read-in any existing uses from apps.

⚠ Since 6.1 shipped with the Newtonsoft Serializer, for testing of the final change, we should make sure we try having a contract serializer with Newtonsoft initialize the SystemInformation storage on the app. Then change to the new serializer and ensure it can read-in all the data to continue from for app migrations.

For more complex app scenarios where devs have done more complex storage, the recommendation is that they provide their own storage helper (as noted above in the issue) for either Newtonsoft or System.Text.Json as they desire.

[michael-hawker]

Before:

Microsoft.Toolkit.Uwp Additional Footprint: 635,580 bytes
  App Diff: (.exe) = 4,096
  App Diff: (.xml) = 264
  App Diff: (.appxsym) = 40,009
  Size Diff: AppxBundleManifest.xml = 11
  Size Diff: AppxBlockMap.xml = 1,190
  Size Diff: AppxManifest.xml = 10
  Size Diff: resources.pri = 104
  Size Diff: System.Runtime.CompilerServices.Unsafe.dll = 1,744
  Additional: Microsoft.Bcl.AsyncInterfaces.dll = 21,064
  Additional: Microsoft.Toolkit.dll = 103,456
  Lib (self): Microsoft.Toolkit.Uwp.dll = 112,672
  Additional: System.Text.Encodings.Web.dll = 57,720
  Additional: System.Text.Json.dll = 293,240
-----------------------------------------

And After (Projected due to #3657):

Microsoft.Toolkit.Uwp Additional Footprint: 263,556 bytes
  App Diff: (.exe) = 4,096
  App Diff: (.xml) = 264
  App Diff: (.appxsym) = 40,009
  Size Diff: AppxBundleManifest.xml = 11
  Size Diff: AppxBlockMap.xml = 1,190
  Size Diff: AppxManifest.xml = 10
  Size Diff: resources.pri = 104
  Size Diff: System.Runtime.CompilerServices.Unsafe.dll = 1,744
  Additional: Microsoft.Toolkit.dll = 103,456
  Lib (self): Microsoft.Toolkit.Uwp.dll = 112,672
-----------------------------------------

Savings of: 372,024 🎉🎉🎉

And since most of our other higher-level packages reference this base package, we'll save this amount on those too!