Documentation/page_tables: Add info about MMU/TLB and Page Faults

Extend page_tables.rst by adding a section about the role of MMU and TLB
in translating between virtual addresses and physical page frames.
Furthermore explain the concept behind Page Faults and how the Linux
kernel handles TLB misses. Finally briefly explain how and why to disable
the page faults handler.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Acked-by: "Mike Rapoport (IBM)" <rppt@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20230818112726.6156-1-fmdefrancesco@gmail.com