docs: reporting-issues.rst: explain how to decode stack traces

Replace placeholder text about decoding stack traces with a section that
properly describes what a typical user should do these days. To make
it works for them, add a paragraph in an earlier section to ensure
people build their kernels with everything that's needed to decode stack
traces later.

Signed-off-by: Thorsten Leemhuis <linux@leemhuis.info>
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/20210215172857.382285-1-linux@leemhuis.info


Signed-off-by: Jonathan Corbet <corbet@lwn.net>