Microsoft.Extensions.AI.Abstractions is raising trim/AOT warnings

[eerhardt]

After #5619 was merged, new warnings are coming from Microsoft.Extensions.AI.Abstractions when trimming/AOT'ing:

    D:\git\extensions\src\Libraries\Microsoft.Extensions.AI.Abstractions\Utilities\AIJsonUtilities.Schema.cs(305): Trim analysis error IL2026: Microsoft.Extensions.AI.AIJsonUtilities.<>c__DisplayClass15_0.<GetJsonSchemaCore>g__TransformSchemaNode|0(JsonSchemaExporterContext,JsonNode): Using member 'System.Text.Json.Nodes.JsonArray.Add<String>(String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Creating JsonValue instances with non-primitive types is not compatible with trimming. It can result in non-primitive types being serialized, which may have their members trimmed. [D:\git\extensions\test\Libraries\Microsoft.Extensions.AotCompatibility.TestApp\Microsoft.Extensions.AotCompatibility.TestApp.csproj]
    D:\git\extensions\src\Libraries\Microsoft.Extensions.AI.Abstractions\Utilities\AIJsonUtilities.Schema.cs(305): AOT analysis error IL3050: Microsoft.Extensions.AI.AIJsonUtilities.<>c__DisplayClass15_0.<GetJsonSchemaCore>g__TransformSchemaNode|0(JsonSchemaExporterContext,JsonNode): Using member 'System.Text.Json.Nodes.JsonArray.Add<String>(String)' which has 'RequiresDynamicCodeAttribute' can break functionality when AOT compiling. Creating JsonValue instances with non-primitive types requires generating code at runtime. [D:\git\extensions\test\Libraries\Microsoft.Extensions.AotCompatibility.TestApp\Microsoft.Extensions.AotCompatibility.TestApp.csproj]

cc @eiriktsarpalis

[eerhardt]

Line 305 is what is causing the warning:

extensions/src/Libraries/Microsoft.Extensions.AI.Abstractions/Utilities/AIJsonUtilities.Schema.cs

Lines 303 to 305 in 95a80cc

	if (required is not JsonArray { } requiredArray || requiredArray.Count != propertiesObj.Count)
	{
	requiredArray = [.. propertiesObj.Select(prop => prop.Key)];

@agocke - this is a pretty interesting case of how to evade the Roslyn analyzers. Here, there is no explict call to JsonArray.Add<String>(String). But instead, it is using a collection expression, which is calling .Add under the covers. I wonder if the LDM considered this scenario when designing collection expressions (that Analyzers for the .Add calls won't be triggered).