GH-4272: Allows ValueTypesto be used as Duplicated Fields

[Shield1739]

Problem

ValueTypes used as Duplicated Fields would cause a compilation failure at runtime.

Issue explained in detail in: #4272

Solution

Added support for ValueType members to be used as Duplicated Fields.

• Introduced a new DuplicatedValueTypeField class that encapsulates the ValueType-specific logic for generating correct upsert parameter code, unwrapping the inner primitive Value instead of passing the ValueType wrapper directly.
• Updated DocumentMapping to detect when a duplicated member implements IValueTypeMember<,> and instantiate DuplicatedValueTypeField instead of the standard DuplicatedField, using the registered ValueTypeInfo from StoreOptions.ValueTypes.
• Fixed CreateComparison(...) method to correctly handle LINQ query comparisons against duplicated ValueType fields.

Note: This solution requires the ValueType to be explicitly registered to Marten, e.g opts.RegisterValueType<T>().

Tests

• Added tests for duplicated ValueType fields using Vogen and StronglyTypedId value objects.