kernel.h is being used as a dump for all kinds of stuff for a long time.
Here is the attempt to start cleaning it up by splitting out panic and
oops helpers.

There are several purposes of doing this:
- dropping dependency in bug.h
- dropping a loop by moving out panic_notifier.h
- unload kernel.h from something which has its own domain

At the same time convert users tree-wide to use new headers, although for
the time being include new header back to kernel.h to avoid twisted
indirected includes for existing users.

[akpm@linux-foundation.org: thread_info.h needs limits.h]
[andriy.shevchenko@linux.intel.com: ia64 fix]
  Link: https://lkml.kernel.org/r/20210520130557.55277-1-andriy.shevchenko@linux.intel.com

Link: https://lkml.kernel.org/r/20210511074137.33666-1-andriy.shevchenko@linux.intel.comSigned-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: NBjorn Andersson <bjorn.andersson@linaro.org>
Co-developed-by: NAndrew Morton <akpm@linux-foundation.org>
Acked-by: NMike Rapoport <rppt@linux.ibm.com>
Acked-by: NCorey Minyard <cminyard@mvista.com>
Acked-by: NChristian Brauner <christian.brauner@ubuntu.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NKees Cook <keescook@chromium.org>
Acked-by: NWei Liu <wei.liu@kernel.org>
Acked-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Acked-by: NSebastian Reichel <sre@kernel.org>
Acked-by: NLuis Chamberlain <mcgrof@kernel.org>
Acked-by: NStephen Boyd <sboyd@kernel.org>
Acked-by: NThomas Bogendoerfer <tsbogend@alpha.franken.de>
Acked-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>