Outliner: Add debugging utility to print an elements path

No user visible changes expected.

Adds a function that prints the "path" of an element, that is, the
ancestor elements starting from the root, separated by slashes. This can
be useful for debugging. The function isn't used.

source/blender/editors/space_outliner/tree/tree_element.cc

@@ -4,6 +4,9 @@
  * \ingroup spoutliner
  */
 
+#include <string>
+#include <string_view>
+
 #include "DNA_anim_types.h"
 #include "DNA_listBase.h"
 #include "DNA_space_types.h"
@@ -111,6 +114,17 @@ std::optional<BIFIconID> AbstractTreeElement::getIcon() const
   return {};
 }
 
+void AbstractTreeElement::print_path()
+{
+  std::string path = legacy_te_.name;
+
+  for (TreeElement *parent = legacy_te_.parent; parent; parent = parent->parent) {
+    path = parent->name + std::string_view("/") + path;
+  }
+
+  std::cout << path << std::endl;
+}
+
 void AbstractTreeElement::uncollapse_by_default(TreeElement *legacy_te)
 {
   if (!TREESTORE(legacy_te)->used) {

source/blender/editors/space_outliner/tree/tree_element.hh

@@ -74,6 +74,16 @@ class AbstractTreeElement {
    */
   virtual std::optional<BIFIconID> getIcon() const;
 
+  /**
+   * Debugging helper: Print effective path of this tree element, constructed out of the
+   * #TreeElement.name of each element. E.g.:
+   * - Lorem
+   *   - ipsum dolor sit
+   *     - amet
+   * will print: Lorem/ipsum dolor sit/amet.
+   */
+  void print_path();
+
   /**
    * Expand this tree element if it is displayed for the first time (as identified by its
    * tree-store element).