power-assert context formatter

Create function to format powerAssertContext object provided by power-assert at runtime. Version 1.2.0 is stable. Part of the power-assert-runtime ecosystem. Replaces legacy format function with configurable renderers. Allows custom renderer arrays, reducers, output offset, and line separator. Supports legacy renderer compatibility. Key differentiator: separates formatting concern from assertion, enabling detailed diff diagrams and comparison output.