Complete formatter serialization cleanup (#3596)

[xuzhg]

Remove the obsolete BinaryFormatter round-trip test and its legacy and .NET Core project references. The formatter constructors, GetObjectData overrides, Serializable attributes, warning suppressions, and public API entries were already removed from dev-9.x by #3334.

Remove the remaining NonSerialized annotations from response fields now that their containing exception types no longer support formatter serialization.

The reason to remove  [NonSerialized]  is cleanup and accuracy, not because the attribute itself is unsafe:

•  [NonSerialized]  tells formatter-based serializers to exclude a field from serialization.
• These exception classes are no longer  [Serializable]  and no longer expose serialization constructors or  GetObjectData .
• Therefore, the response fields cannot participate in formatter serialization, making  [NonSerialized]  functionally inert.
• Leaving it suggests that formatter serialization is still supported and that the field requires special serialization treatment.
• Removing it completes the cleanup described in #3596 without changing runtime behavior or public APIs.

References:

• Issue: #3596
•  [NonSerialized]  documentation: https://learn.microsoft.com/dotnet/api/system.nonserializedattribute
• Microsoft BinaryFormatter guidance: https://learn.microsoft.com/dotnet/standard/serialization/binaryformatter-security-guide

Issues

This pull request fixes #xxx.

Description

Briefly describe the changes of this pull request.

Checklist (Uncheck if it is not completed)

• Test cases added
• Build and test with one-click build and test script passed

Additional work necessary

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[Copilot]

Pull request overview

This PR completes the cleanup of legacy formatter-based (e.g., BinaryFormatter) serialization remnants in the OData Client test suite and exception types, aligning with the removal of serialization constructors/GetObjectData/[Serializable] work previously done in #3334 and the goals in issue #3596.

Changes:

• Removes the obsolete BinaryFormatter round-trip unit test for DataServiceClientException.
• Cleans up test project .csproj references that previously included/excluded that test file.
• Removes now-inert [NonSerialized] annotations from response fields in client exception types that no longer support formatter serialization.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/FunctionalTests/Tests/DataServices/UnitTests/Client.TDD.Tests/Tests/DataServiceClientExceptionSerializationTests.cs	Deletes the obsolete BinaryFormatter-based serialization test.
test/FunctionalTests/Tests/DataServices/UnitTests/Client.TDD.Tests/Microsoft.OData.Client.TDDUnitTests.NetCore.csproj	Removes now-unneeded compile-removal entry for the deleted test file.
test/FunctionalTests/Tests/DataServices/UnitTests/Client.TDD.Tests/Microsoft.OData.Client.TDDUnitTests.csproj	Removes compile include for the deleted test file to avoid build break.
src/Microsoft.OData.Client/DataServiceRequestException.cs	Removes inert [NonSerialized] from the response field.
src/Microsoft.OData.Client/DataServiceQueryException.cs	Removes inert [NonSerialized] from the response field.

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[xuzhg]

/AzurePipelines run