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>

3 files changed, 0 insertions, 0 deletions

diff --git a/documentation/dev-manual/figures/devtool-add-flow.png b/documentation/dev-manual/figures/devtool-add-flow.png
new file mode 100644
index 0000000000..e7d6173d2d
--- /dev/null
+++ b/documentation/dev-manual/figures/devtool-add-flow.png
diff --git a/documentation/dev-manual/figures/devtool-modify-flow.png b/documentation/dev-manual/figures/devtool-modify-flow.png
new file mode 100644
index 0000000000..18ba8b7e65
--- /dev/null
+++ b/documentation/dev-manual/figures/devtool-modify-flow.png
diff --git a/documentation/dev-manual/figures/devtool-upgrade-flow.png b/documentation/dev-manual/figures/devtool-upgrade-flow.png
new file mode 100644
index 0000000000..7d4f395e24
--- /dev/null
+++ b/documentation/dev-manual/figures/devtool-upgrade-flow.png