docs: scheduler: convert docs to ReST and rename to *.rst

In order to prepare to add them to the Kernel API book,
convert the files to ReST format.

The conversion is actually:
  - add blank lines and identation in order to identify paragraphs;
  - fix tables markups;
  - add some lists markups;
  - mark literal blocks;
  - adjust title markups.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/ABI/testing/sysfs-kernel-uids

@@ -11,4 +11,4 @@ Description:
 		example would be, if User A has shares = 1024 and user
 		B has shares = 2048, User B will get twice the CPU
 		bandwidth user A will. For more details refer
-		Documentation/scheduler/sched-design-CFS.txt
+		Documentation/scheduler/sched-design-CFS.rst