Move devtool doc from extensible to dev manual

[YOCTO #13417]

devtool is not directly tied to the Extensible SDK anymore, and
instructions in there can be split and added to the development manual.

This patch is a simple bulk move, except for the following:

- Intro added to the devtool.rst document (mostly copy-pasted from the
  devtool quick reference in the ref-manual).
- Figures renamed to remove "sdk-" from filenames.
- References to sdk-manual/extensible replaced by dev-manual/devtool.

Reported-By: Paul Eggleton <bluelightning@bluelightning.org>
(From yocto-docs rev: 044d3185b858fce1febcfe3a6834b883f9a598fa)

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

documentation/dev-manual/index.rst

@@ -23,6 +23,7 @@ Yocto Project Development Tasks Manual
    speeding-up-build
    libraries
    prebuilt-libraries
+   devtool
    x32-psabi
    gobject-introspection
    external-toolchain

documentation/dev-manual/new-recipe.rst

@@ -56,7 +56,7 @@ necessary when adding a recipe to build a new piece of software to be
 included in a build.
 
 You can find a complete description of the ``devtool add`` command in
-the ":ref:`sdk-manual/extensible:a closer look at \`\`devtool add\`\``" section
+the ":ref:`dev-manual/devtool:a closer look at \`\`devtool add\`\``" section
 in the Yocto Project Application Development and the Extensible Software
 Development Kit (eSDK) manual.
 

documentation/dev-manual/upgrading-recipes.rst

@@ -203,7 +203,7 @@ As mentioned earlier, an alternative method for upgrading recipes to
 newer versions is to use
 :doc:`devtool upgrade </ref-manual/devtool-reference>`.
 You can read about ``devtool upgrade`` in general in the
-":ref:`sdk-manual/extensible:use \`\`devtool upgrade\`\` to create a version of the recipe that supports a newer version of the software`"
+":ref:`dev-manual/devtool:use \`\`devtool upgrade\`\` to create a version of the recipe that supports a newer version of the software`"
 section in the Yocto Project Application Development and the Extensible
 Software Development Kit (eSDK) Manual.