admin-guide: merge oops-tracing with bug-hunting

Now that oops-tracing.rst has only information about
stack dumps found on OOPS, and bug-hunting.rst has only
information about how to identify the source code line
associated with a stack dump, let's merge them and
improve the information inside it.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/index.rst

@@ -27,7 +27,6 @@ problems and bugs in particular.
    security-bugs
    bug-hunting
    bug-bisect
-   oops-tracing
    tainted-kernels
    ramoops
    dynamic-debug-howto