.Net ContextVariables is replaced by KernelFunctionArguments

[SergeyMenshykh]

Closes - #3689 and #3690

The PR introduces the following changes:

• The 'ContextVariables' class has been removed. Previously, this class was used by kernel functions as a property bag, where functions could resolve their arguments and store their outputs. By removing this class and introducing the 'KernelFunctionArguments' class, the function calling pattern for SK functions now resembles a more familiar and convenient approach, where functions accept a list of arguments and return a result, rather than working with and mutating a property bag.
• The functionality for converting function results from objects to strings has been moved from the 'KernelFunctionFromMethod' class to the 'FunctionResult' class. This change is a step towards enabling SK to work with complex types, rather than just strings. Currently, SK can only work with strings, and it is not possible to save the string representation of results in context variables anymore. Therefore, the conversion functionality has been moved to the 'FunctionResult' class until support for complex types is added to SK.