Refactor `activate()` to use `await`

[datho7561]

Refactor the activate function (main entry point to extension) to use await instead of promise chaining and promise constructors.

Why?

• The async logic is currently really hard to read
• The function is > 300 lines of code, and using async could make it shorter
• The function contains async promise executors, which are considered bad since they make error handling hard