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 <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>

Documentation/vm/numa.rst

@@ -99,7 +99,7 @@ Local allocation will tend to keep subsequent access to the allocated memory
 as long as the task on whose behalf the kernel allocated some memory does not
 later migrate away from that memory.  The Linux scheduler is aware of the
 NUMA topology of the platform--embodied in the "scheduling domains" data
-structures [see Documentation/scheduler/sched-domains.txt]--and the scheduler
+structures [see Documentation/scheduler/sched-domains.rst]--and the scheduler
 attempts to minimize task migration to distant scheduling domains.  However,
 the scheduler does not take a task's NUMA footprint into account directly.
 Thus, under sufficient imbalance, tasks can migrate between nodes, remote