Add benchmarking for @authx/scopes

[mike-marcacci]

The functions in this utility are often in reasonably hot paths, both in this project and in directly-consuming projects. These were written with a focus on correctness over performance, and building a benchmark would:

• give us a better sense of the computational cost associated with these functions
• bring attention to any particularly poor-performing functions or scenarios
• allow us to better assess the performance impact of any changes proposed to these functions