docs: reporting-issues: create a proper appendix explaining specialties

docs: reporting-issues: create a proper appendix explaining specialties

Merge "Why some bugs remain unfixed and some reports are ignored" with
the closing words while rewriting and extending the text.

The result spends fewer words on explaining things that are normal in
FLOSS -- while outlining where the kernel is different and how that
makes bug reporting more complicated than in other FLOSS projects.

Signed-off-by: Thorsten Leemhuis <linux@leemhuis.info>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <473b36fa9723c46b7167004752f097e6c26d7278.1773750701.git.linux@leemhuis.info>