depot_tools: move under src/chromium/

We've moved all the other repos to src/chromium/, so move over this
last one.  We duplicate it for now so we can update existing users.

BUG=None
TEST=precq passes

Change-Id: I8b986c7dfa79a650aa291475714241d03b269fc1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/manifest/+/1832724Reviewed-by: Michael Mortensen <mmortensen@google.com>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>

full.xml

@@ -429,6 +429,11 @@ Your sources have been sync'd successfully.
   <!-- Please keep depot_tools pin in sync with our build recipe at:
     https://cs.chromium.org/chromium/build/scripts/slave/recipe_modules/chromite/api.py
     -->
+  <project path="src/chromium/depot_tools"
+           name="chromium/tools/depot_tools"
+           revision="3841eaa164c2f34c8ea969d462a3151b10151780"
+           remote="chromium"
+           groups="minilayout,firmware,buildtools,labtools" />
   <project path="chromium/tools/depot_tools"
            name="chromium/tools/depot_tools"
            revision="3841eaa164c2f34c8ea969d462a3151b10151780"