20211110 adjusts getting-started documentation for Raspbian bullseye

The `libseccomp2` patch recommended for Raspbian Buster is not needed
for Bullseye (the updated version is already in place).

Installing the patch recommended for Buster breaks Bullseye
installations so it is to be avoided.

Also:

* expands on pre-requisites
* adds note that PiZeroW2 will run IOTstack
* adds style tags (bash, yaml, etc) to code fences
* changes some multi-step commands to use single-step equivalents
(eg `stop` then `rm -rf` replaced with `rm --force --stop -v`)
* rewrites the "nuclear option" to be less destructive while achieving
the same outcome.

Author: Paraphraser