Create `IOperationResult` assert extensions

[Carl-Hugo]

Allow easy testing of IOperationResult with default failure message.

Examples:

result.AssertSuccess(); // Failure message: The operation should be sucessful.
result.AssertFailure(); // Failure: The operation should not be sucessful.
result.AssertFailure(
    error => Assert.Equal("Some expected error message 1", error.Message),
    error => Assert.Equal("Some expected error message 2", error.Message),
    error => Assert.Equal("Some expected error message ...", error.Message),
    error => Assert.Equal("Some expected error message N", error.Message)
);
// Failure: The operation should not be sucessful.
// Collection failure: report (do not handle) Assert.Collection() error