Re-design of submodules used in blender.git

This commit implements described in the #104573.

The goal is to fix the confusion of the submodule hashes change, which are not
ideal for any of the supported git-module configuration (they are either always
visible causing confusion, or silently staged and committed, also causing
confusion).

This commit replaces submodules with a checkout of addons and addons_contrib,
covered by the .gitignore, and locale and developer tools are moved to the
main repository.

This also changes the paths:
- /release/scripts are moved to the /scripts
- /source/tools are moved to the /tools
- /release/datafiles/locale is moved to /locale

This is done to avoid conflicts when using bisect, and also allow buildbot to
automatically "recover" wgen building older or newer branches/patches.

Running `make update` will initialize the local checkout to the changed
repository configuration.

Another aspect of the change is that the make update will support Github style
of remote organization (origin remote pointing to thy fork, upstream remote
pointing to the upstream blender/blender.git).

Pull Request #104755

scripts/modules/bpy/utils/previews.py

@@ -0,0 +1,137 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+"""
+This module contains utility functions to handle custom previews.
+
+It behaves as a high-level 'cached' previews manager.
+
+This allows scripts to generate their own previews, and use them as icons in UI widgets
+('icon_value' for UILayout functions).
+
+
+Custom Icon Example
+-------------------
+
+.. literalinclude:: __/__/__/scripts/templates_py/ui_previews_custom_icon.py
+"""
+
+__all__ = (
+    "new",
+    "remove",
+    "ImagePreviewCollection",
+)
+
+import _bpy
+_utils_previews = _bpy._utils_previews
+del _bpy
+
+
+_uuid_open = set()
+
+
+# High-level previews manager.
+# not accessed directly
+class ImagePreviewCollection(dict):
+    """
+    Dictionary-like class of previews.
+
+    This is a subclass of Python's built-in dict type,
+    used to store multiple image previews.
+
+    .. note::
+
+        - instance with :mod:`bpy.utils.previews.new`
+        - keys must be ``str`` type.
+        - values will be :class:`bpy.types.ImagePreview`
+    """
+
+    # Internal notes:
+    # - Blender's internal 'PreviewImage' struct uses 'self._uuid' prefix.
+    # - Blender's preview.new/load return the data if it exists,
+    #   don't do this for the Python API as it allows accidental re-use of names,
+    #   anyone who wants to reuse names can use dict.get() to check if it exists.
+    #   We could use this for the C API too (would need some investigation).
+
+    def __init__(self):
+        super().__init__()
+        self._uuid = hex(id(self))
+        _uuid_open.add(self._uuid)
+
+    def __del__(self):
+        if self._uuid not in _uuid_open:
+            return
+
+        raise ResourceWarning(
+            "%r: left open, remove with 'bpy.utils.previews.remove()'" % self
+        )
+        self.close()
+
+    def _gen_key(self, name):
+        return ":".join((self._uuid, name))
+
+    def new(self, name):
+        if name in self:
+            raise KeyError("key %r already exists" % name)
+        p = self[name] = _utils_previews.new(
+            self._gen_key(name))
+        return p
+    new.__doc__ = _utils_previews.new.__doc__
+
+    def load(self, name, path, path_type, force_reload=False):
+        if name in self:
+            raise KeyError("key %r already exists" % name)
+        p = self[name] = _utils_previews.load(
+            self._gen_key(name), path, path_type, force_reload)
+        return p
+    load.__doc__ = _utils_previews.load.__doc__
+
+    def clear(self):
+        """Clear all previews."""
+        for name in self.keys():
+            _utils_previews.release(self._gen_key(name))
+        super().clear()
+
+    def close(self):
+        """Close the collection and clear all previews."""
+        self.clear()
+        _uuid_open.remove(self._uuid)
+
+    def __delitem__(self, key):
+        _utils_previews.release(self._gen_key(key))
+        super().__delitem__(key)
+
+    def __repr__(self):
+        return "<%s id=%s[%d], %r>" % (
+            self.__class__.__name__, self._uuid, len(self), super()
+        )
+
+
+def new():
+    """
+    :return: a new preview collection.
+    :rtype: :class:`ImagePreviewCollection`
+    """
+
+    return ImagePreviewCollection()
+
+
+def remove(pcoll):
+    """
+    Remove the specified previews collection.
+
+    :arg pcoll: Preview collection to close.
+    :type pcoll: :class:`ImagePreviewCollection`
+    """
+    pcoll.close()
+
+
+# don't complain about resources on exit (only unregister)
+import atexit
+
+
+def exit_clear_warning():
+    del ImagePreviewCollection.__del__
+
+
+atexit.register(exit_clear_warning)
+del atexit, exit_clear_warning

scripts/modules/bpy/utils/toolsystem.py

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# Until we untangle ToolDef from bl_ui internals,
+# use this module to document ToolDef.
+from bl_ui.space_toolsystem_common import ToolDef