[enhancement] Review our dependencies (especially in requirements.txt)

From: c3c40c72

AS has been around for a while, and some of its dependencies are legacy from a time it required older versions of Python. We can review the differences between requirements.txt and setup.* (or maybe even choose to drop requirements.txt?), and remove unnecessary dependencies, as well as upgrade the ones that we are actively using.

This might give us some improvement in the time to install and to build the project, but it is also a good security practice (less dependencies, less points to look for vulnerabilities).