Anim: DNA for `Animation` data-block

Introduce new DNA for the `Animation` data-block and its sub-data.

This includes the blenkernel code for reading & writing to blend files,
and for memory management (freeing, duplicating). Minimal C++ wrappers
are included, with just the functionality needed for blenkernel to do
its job.

The Outliner code is extended so that it knows about the new data-type,
nothing more.

For more info, see issue #113594.

@@ -0,0 +1,291 @@
+/* SPDX-FileCopyrightText: 2023 Blender Developers

@@ -0,0 +132,4 @@
+class Layer : public ::AnimationLayer {
+ public:
+  Layer() = default;
+  Layer(const Layer &other);

@@ -0,0 +148,4 @@
+
+  enum class MixMode : int8_t {
+    Replace = 0,
+    Offset = 1,

@@ -0,0 +215,4 @@
+/**
+ * Bag of F-Curves for a specific Output handle.
+ */
+class ChannelBag : public ::AnimationChannelBag {

@@ -1211,0 +1401,4 @@
+  int32_t output_handle;
+
+  int fcurve_array_num;
+  FCurve **fcurve_array; /* Array of 'fcurve_array_num' FCurves. */

@@ -0,0 +205,4 @@
+    /*main_listbase_index*/ INDEX_ID_AN,
+    /*struct_size*/ sizeof(Animation),
+    /*name*/ "Animation",
+    /*name_plural*/ "animations",

@@ -0,0 +59,4 @@
+  /**
+   * Duplicate all Animation data from 'other' into `this`.
+   *
+   * Only used by the ID datablock management, other code should use regular ID

@@ -0,0 +119,4 @@
+   */
+  Type type() const
+  {
+    return static_cast<Type>(this->strip_type);

@@ -0,0 +204,4 @@
+
+template<> bool Strip::is<KeyframeStrip>() const
+{
+  return type() == Type::Keyframe;

@@ -0,0 +7,4 @@
+ */
+
+#include "BLI_listbase.h"
+#include "BLI_listbase_wrapper.hh"

@@ -0,0 +27,4 @@
+
+#include "BLT_translation.hh"
+
+using namespace blender;

@@ -0,0 +47,4 @@
+/** Free (or release) any data used by this animation (does not free the animation itself). */
+static void animation_free_data(ID *id)
+{
+  ((Animation *)id)->wrap().free_data();

@@ -0,0 +30,4 @@
+
+namespace blender::bke {
+
+/** Deep copy an Animation data-block. */

@@ -0,0 +31,4 @@
+namespace blender::bke {
+
+/** Deep copy an Animation data-block. */
+static void animation_copy_data(Main * /*bmain*/, ID *id_dst, const ID *id_src, const int /*flag*/)

@@ -1149,0 +1178,4 @@
+   * another Animation data-block.
+   *
+   * \see AnimationOutput::name */
+  char output_name[66];

@@ -1211,0 +1282,4 @@
+ * \see blender::animrig::Layer
+ */
+typedef struct AnimationLayer {
+  /** User-Visible identifier, unique within the Animation. `MAX_ID_NAME - 2`. */