Documentation: Updated installation and contribution documentation

[t20100]

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• [x] The PR title is formatted as: <Module or Topic>: <Action> <Summary> (see contributing guidelines)

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This PR reworks and moves/removes documentation regarding installation and contribution.

Some of the content was outdated or is better documented elsewhere (e.g., use of virtual environment: https://packaging.python.org/en/latest/guides/installing-using-pip-and-virtual-environments/#create-and-use-virtual-environments).

closes #4125