[PP-1] Update all comments and documentation in Project Browser to refer to "sandboxes" and related terminology

Problem/Motivation

The followup to 📌 Adjust project_browser to the class renaming changes in package_manager Active . That issue was only about matching the class renames in core's Package Manager module. Comments or documentation hasn't been touched in that issue, those changes should happen within this issue.

Steps to reproduce

Proposed resolution