Add support for array encoding with @encode(ArrayEncoding.*) decorator

[radhgupta]

This pull request adds support for custom array encoding formats in the C# HTTP client generator, allowing arrays to be serialized and deserialized using delimiters such as comma, space, pipe, or newline. The changes span the model, serialization logic, type conversion, and test coverage to ensure correct handling of these encodings.

Array encoding support

• Introduced an optional encode property to InputModelProperty and related types to specify the desired array encoding (e.g., commaDelimited, spaceDelimited, etc.). This is reflected in the type definitions, model constructors, and JSON serialization/deserialization logic.
• Updated the type converter (type-converter.ts) to propagate the encode property from SDK model properties into the input model.

Serialization and deserialization logic

• Added custom serialization and deserialization methods in MrwSerializationTypeDefinition.cs to handle arrays with specified encodings. These methods join or split array elements using the appropriate delimiter and handle both string and primitive element types.

Test coverage

• Added new tests in EncodeArrayTests.cs to verify correct serialization and deserialization for each supported encoding format (comma, space, pipe, newline).

Implements: #9028

[github-actions]

No changes needing a change description found.

[jorgerangel-msft]

It's good to see the spector tets, but could we also please add some unit tests for the serialization + deserialization code? It would be helpful to see the generated output of that.

[jorgerangel-msft]

As Josh pointed out, I think these encoding formats should be an enum type.