fix:Property set expression builder does not accept null values and lambdas

[ivo-stoilov]

closes telerik/MATTeam#905

[Copilot]

Pull Request Overview

This PR enhances the property expression builder to accept null constants and lambda expressions for setting values, and updates related docs and error messaging.

• Specify the target type in Expression.Constant to allow null values.
• Introduce a Set(Expression<Func<T>>) overload for setting via lambda.
• Refine error messages in ArrangeSet and improve XML documentation in interfaces and Expr utility.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
PropertyExpressionBuilder.cs	Added typeof(T) to constant expression and new Set(Expression<Func<T>>) overload.
Mock.Arrange.cs	Clarified ArrangeSet(Action) error text and updated usage examples.
IPropertyExpressionBuilder.cs	Added overload and expanded XML docs for both Set methods and Get.
Expr.cs	Switched to ArgumentException for invalid expressions and enriched XML documentation.

Comments suppressed due to low confidence (2)

Telerik.JustMock/PropertyExpressionBuilder.cs:46

• Add unit tests for the new Set(Expression<Func<T>>) overload, including cases with null inputs and various lambda bodies, to validate its behavior.

public Expression<Action> Set(Expression<Func<T>> expression)

Telerik.JustMock/Mock.Arrange.cs:161

• Update or add tests to assert the updated ArrangeSet error message and example formatting when OnDemand is enabled, preventing future regressions in output.

sb.AppendLine("ArrangeSet(Action) is not compatible with the OnDemand feature.");