overview-manual: convert patching.png to svg

- Convert the png file to an SVG file.
- Add the new UNPACKDIR directory to the image.
- Remove ${PR} from WORKDIR value, after cc83e4548465 ("bitbake.conf:
  Drop PE and PR from WORKDIR and STAMP") on OE-Core.
- Change S value to BP (equal to ${BPN}-${PV}, but more accurate).-

Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
(From yocto-docs rev: 73b6c0c5e5470d4a929fd3d5cde6d4fb0ace53b8)

Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/overview-manual/concepts.rst

@@ -764,7 +764,7 @@ Patching
 Once source code is fetched and unpacked, BitBake locates patch files
 and applies them to the source files:
 
-.. image:: figures/patching.png
+.. image:: svg/patching.*
    :width: 100%
 
 The :ref:`ref-tasks-patch` task uses a