Replace usage of xcpretty with xcbeautify

[pereBohigas]

Is your feature request related to a problem? Please describe.
It seems that xcpretty is not being actively developed. As it is mainly written in Ruby, which has declined in popularity lately, the future of its development is uncertain.

Describe the solution you'd like
The Swift community is moving towards the use of xcbeautify, which integrates nicely with GitHub Actions. As this one is written in Swift, it is therefore more future-proof.

Thank you so much for maintaining Amethyst!!