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ARROW-15623: [C++][Python] Update developers/python.rst (console blocks + "" in archery install)

This PR updates the _developers/python.rst_ page with:

- use of console blocks instead of shell (when selecting the code text prompts are excluded),
- adding "" to the archery install comand,

It also adds `sphinx-copybutton` extension enabling the user to copy the content of the `code-block` with a copy button.

Closes #12485 from AlenkaF/ARROW-15623

Lead-authored-by: "Alenka Frim <frim.alenka@gmail.com>"
Co-authored-by: Alenka Frim <AlenkaF@users.noreply.github.com>
Co-authored-by: Alenka Frim <frim.alenka@gmail.com>
Signed-off-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>