docs: improve documentation

[leahaeusel]

Description and Context:
What and Why?

This PR improves our documentation by:

• displaying the __init__() methods in the documentation (the information in these docstrings was not visible in the documentation so far)
• removing the tab 'queens packages' from the main menu in the top bar (Is redundant because of the 'Packages' tab):
  Before:

After:

• placing the types indicated by type hinting where the types from the docstrings are (makes function signature more easily readable):
  Before:

After:

• fixing bugs in the docstrings which sphinx complained about but we silently ignored so far (mostly related to lists)
• updating the instructions on how to build the documentation locally
• updating the onboarding tutorial
• removing doc/source/_ext/templates/1-monte_carlo_uq.rst.j2, which is no longer needed

Related Issues and Pull Requests

• Closes
• Related to

Interested Parties

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