[DOCS]: create dropdown output in documentation

[shahzebsiddiqui]

Documentation Link

https://buildtest.readthedocs.io/en/devel/installing_buildtest.html#usage-buildtest-help

Issue Description

So there is a feature to enable dropdown output text via https://sphinx-design.readthedocs.io/en/latest/dropdowns.html# which can be used to condense long output, mentioned by @etpalmer63. This could be useful where output is generated with --help such as buildtest --help or buildtest <subcommand> --help

Let's try to use this dropdown and update the documentation accordingly.

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