docs: submit-checklist: structure by category

While going through the submit checklist, the list order seemed rather
random, probably just by historical coincidences of always adding yet the
next point someone thought of at the end of the list.

Structure and order them by the category of such activity,
reviewing, documenting, checking with tools, building and testing.

As the diff of the reordering is large:
Review code now includes previous points 1, 5 and 22.
Review Kconfig includes previous 6, 7 and 8.
Documenting includes previous 11, 15, 16, 17, 18 and 23.
Checking with tools includes previous 5, 9 and 10.
Building includes previous 2, 3, 20 and 24.
Testing includes previous 12, 13, 14, 19 and 21.

Previous point 4 (compile for ppc64) was merged into point 3 (build for
many architectures), as it was just a further note to cross-compiling.

Previous point 5 was split into one in review and one in checking
to have every previous point in the right category.
Point 11 was shortened, as building documentation is mentioned already
in Build your code, 1d.

A note that was presented visually much too aggressive in the HTML view was
turned into a simple "Note that..." sentence in the enumeration.

The recommendation to test with the -mm patchset (previous 21, now
testing, point 5) was updated to the current state of affairs to test with
a recent tag of linux-next.

Note that the previous first point still remains the first list even after
reordering. Randy confirmed that it was important to Stephen Rothwell to
keep 'include what you use' to be the first in the list.

While at it, replace the reference to the obsolete CONFIG_DEBUG_SLAB with
CONFIG_SLUB_DEBUG.

Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20240229030743.9125-2-lukas.bulwahn@gmail.com>