test: fix serialization tests on Windows

[wlsnmrk]

Serialization tests (Chickensoft.LogicBlocks.Tests.Serialization.LogicBlockSerialization.SerializesLogicBlock and Chickensoft.LogicBlocks.Tutorial.Tests.SerializableLogicBlockTests.Serializes) fail on Windows:

This is because the generated JSON has CRLF line endings on Windows, but the expected string literal has LF:

This change uses JsonNode.DeepEquals() to compare expected and generated JSON strings, avoiding whitespace issues generally, as recommended in the proposal discussion for the forthcoming JsonSerializerOptions.NewLine property.