docs: make reporting-bugs.rst obsolete

Make various places which point to
Documentation/admin-guide/reporting-bugs.rst point to
Documentation/admin-guide/reporting-issues.rst instead. That document is
brand new and as of now is not completely finished. But even at this
stage it's a lot more helpful and accurate than reporting-bugs.rst.
Hence also add a note to reporting-bugs.rst, telling people they're
better off reading reporting-issues.rst instead.

reporting-bugs.rst is scheduled for removal once reporting-issues.rst
is considered ready.

Signed-off-by: Thorsten Leemhuis <linux@leemhuis.info>
Link: https://lore.kernel.org/r/3df7c2d16de112b47bb6e6158138608e78562bf5.1607063223.git.linux@leemhuis.info


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