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>

init/Kconfig

@@ -734,7 +734,7 @@ menuconfig CGROUPS
 	  use with process control subsystems such as Cpusets, CFS, memory
 	  controls or device isolation.
 	  See
-		- Documentation/scheduler/sched-design-CFS.txt	(CFS)
+		- Documentation/scheduler/sched-design-CFS.rst	(CFS)
 		- Documentation/cgroup-v1/ (features for grouping, isolation
 					  and resource control)
 
@@ -835,7 +835,7 @@ config CFS_BANDWIDTH
 	  tasks running within the fair group scheduler.  Groups with no limit
 	  set are considered to be unconstrained and will run with no
 	  restriction.
-	  See Documentation/scheduler/sched-bwc.txt for more information.
+	  See Documentation/scheduler/sched-bwc.rst for more information.
 
 config RT_GROUP_SCHED
 	bool "Group scheduling for SCHED_RR/FIFO"
@@ -846,7 +846,7 @@ config RT_GROUP_SCHED
 	  to task groups. If enabled, it will also make it impossible to
 	  schedule realtime tasks for non-root users until you allocate
 	  realtime bandwidth for them.
-	  See Documentation/scheduler/sched-rt-group.txt for more information.
+	  See Documentation/scheduler/sched-rt-group.rst for more information.
 
 endif #CGROUP_SCHED