refactor(core): clean up constructor & extension setup in extension manager

[bdbch]

Please describe your changes

This PR restructures the code of the extension manager by:

1. Moving the extension setup loop into it's own function cleaning up the constructor for better clarity and understanding
2. Restructured the component event listener setup to first get all extension fields and afterwards binding the listeners from the extension fields

I also added a few comments to better describe what some functions are doing.

How did you accomplish your changes

See above

How have you tested your changes

Did a local test and all functionalities were behaving the same.

Checklist

• The changes are not breaking the editor
• Added tests where possible
• Followed the guidelines
• Fixed linting issues

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[nperez0111]

lgtm