feat: add support for go-cmp argument matching

[IlyasYOY]

Summary

Added support for Google's go-cmp library in the mock package for customizable deep comparisons during test assertions:

• Updated go.mod to include go-cmp dependency
• Introduced goCmpArgument type in mock/mock.go to encapsulate comparison values and options
• Implemented GoCmp() helper function to create comparison arguments
• Use cmp.Diff() for precise comparison output
• Allow customization via cmp.Options

Changes

Adds new assertion behavior (not a bug fix):

• Introduces GoCmp() as an alternative to mock.MatchedBy()
• Enables field-level comparison customization via cmp.Option
• Adds diff output formatting in error messages

Motivation

Support more precise comparisons than reflect.DeepEqual (e.g., ignoring specific fields)

Example usage

// Basic usage with a map
mock.On("Method", mock.GoCmp(map[string]bool{"test": true}))

// With options for unexported fields
mock.On("Method", mock.GoCmp(&ExampleType{ran: false}, cmp.AllowUnexported(ExampleType{})))

Related issues

Might relate to some issues looking for a better way to match arguments:

• Feature: support user implementations of Match when diffing mock arguments #1695
• Diff on mocking library #1234
• Export mock.argumentMatcher #1002
• mock: add MatchedByRegexp(pattern) #817

[IlyasYOY]

This PR looks like very much like #579 (but for the mock module).