feat(common): support null value for reference type collection elements (#3163)

- update `SerializationBuilder` to set `ValueSerialization.IsNullable : true` for reference type collection elements
  - that will add null value handling in deserialization logic for collection elements of reference type
- generate null check in generated serialization/deserialization codes for:
  - nullable value type
  - list/dictionary types
  - some framework reference types
- optimize null value processing so that we don't generate null check codes
  - for custom model types, put null value processing logic into the deserialization method of each model
  - for string, use default serialization/deserialization methods which can handle null value
  - update `byte[]` serializatoin/deserialization methods so that they can handle null value, so that we don't generate null check codes externally
- fix 3 test cases previously do not accept null value in collections in response, now we align with other language implementaion on that

resolve #3159

Author: archerzz

samples/AnomalyDetector/Generated/Models/AlignPolicy.Serialization.cs

@@ -57,6 +57,10 @@ void IUtf8JsonSerializable.Write(Utf8JsonWriter writer)
 
         internal static AlignPolicy DeserializeAlignPolicy(JsonElement element)
         {
+            if (element.ValueKind == JsonValueKind.Null)
+            {
+                return null;
+            }
             Optional<AlignMode?> alignMode = default;
             Optional<FillNAMethod?> fillNAMethod = default;
             Optional<float?> paddingValue = default;

samples/AnomalyDetector/Generated/Models/AnomalyDetectionModel.Serialization.cs

@@ -16,6 +16,10 @@ public partial class AnomalyDetectionModel
     {
         internal static AnomalyDetectionModel DeserializeAnomalyDetectionModel(JsonElement element)
         {
+            if (element.ValueKind == JsonValueKind.Null)
+            {
+                return null;
+            }
             string modelId = default;
             DateTimeOffset createdTime = default;
             DateTimeOffset lastUpdatedTime = default;

samples/AnomalyDetector/Generated/Models/AnomalyInterpretation.Serialization.cs

@@ -15,6 +15,10 @@ public partial class AnomalyInterpretation
     {
         internal static AnomalyInterpretation DeserializeAnomalyInterpretation(JsonElement element)
         {
+            if (element.ValueKind == JsonValueKind.Null)
+            {
+                return null;
+            }
             Optional<string> variable = default;
             Optional<float?> contributionScore = default;
             Optional<CorrelationChanges> correlationChanges = default;

samples/AnomalyDetector/Generated/Models/AnomalyState.Serialization.cs

@@ -17,6 +17,10 @@ public partial class AnomalyState
     {
         internal static AnomalyState DeserializeAnomalyState(JsonElement element)
         {
+            if (element.ValueKind == JsonValueKind.Null)
+            {
+                return null;
+            }
             DateTimeOffset timestamp = default;
             Optional<AnomalyValue> value = default;
             Optional<IReadOnlyList<ErrorResponse>> errors = default;

samples/AnomalyDetector/Generated/Models/AnomalyValue.Serialization.cs

@@ -16,6 +16,10 @@ public partial class AnomalyValue
     {
         internal static AnomalyValue DeserializeAnomalyValue(JsonElement element)
         {
+            if (element.ValueKind == JsonValueKind.Null)
+            {
+                return null;
+            }
             bool isAnomaly = default;
             float severity = default;
             float score = default;

samples/AnomalyDetector/Generated/Models/CorrelationChanges.Serialization.cs

@@ -16,6 +16,10 @@ public partial class CorrelationChanges
     {
         internal static CorrelationChanges DeserializeCorrelationChanges(JsonElement element)
         {
+            if (element.ValueKind == JsonValueKind.Null)
+            {
+                return null;
+            }
             Optional<IReadOnlyList<string>> changedVariables = default;
             foreach (var property in element.EnumerateObject())
             {

samples/AnomalyDetector/Generated/Models/DiagnosticsInfo.Serialization.cs

@@ -37,6 +37,10 @@ void IUtf8JsonSerializable.Write(Utf8JsonWriter writer)
 
         internal static DiagnosticsInfo DeserializeDiagnosticsInfo(JsonElement element)
         {
+            if (element.ValueKind == JsonValueKind.Null)
+            {
+                return null;
+            }
             Optional<ModelState> modelState = default;
             Optional<IList<VariableState>> variableStates = default;
             foreach (var property in element.EnumerateObject())

samples/AnomalyDetector/Generated/Models/ErrorResponse.Serialization.cs

@@ -25,6 +25,10 @@ void IUtf8JsonSerializable.Write(Utf8JsonWriter writer)
 
         internal static ErrorResponse DeserializeErrorResponse(JsonElement element)
         {
+            if (element.ValueKind == JsonValueKind.Null)
+            {
+                return null;
+            }
             string code = default;
             string message = default;
             foreach (var property in element.EnumerateObject())

samples/AnomalyDetector/Generated/Models/ModelInfo.Serialization.cs

@@ -80,6 +80,10 @@ void IUtf8JsonSerializable.Write(Utf8JsonWriter writer)
 
         internal static ModelInfo DeserializeModelInfo(JsonElement element)
         {
+            if (element.ValueKind == JsonValueKind.Null)
+            {
+                return null;
+            }
             string dataSource = default;
             Optional<DataSchema?> dataSchema = default;
             DateTimeOffset startTime = default;

samples/AnomalyDetector/Generated/Models/ModelState.Serialization.cs

@@ -62,6 +62,10 @@ void IUtf8JsonSerializable.Write(Utf8JsonWriter writer)
 
         internal static ModelState DeserializeModelState(JsonElement element)
         {
+            if (element.ValueKind == JsonValueKind.Null)
+            {
+                return null;
+            }
             Optional<IList<int>> epochIds = default;
             Optional<IList<float>> trainLosses = default;
             Optional<IList<float>> validationLosses = default;