Blender 3.6: Switch SVN to Git submodules using Git-LFS

This change makes it so build system and update utilities for Blender builds
are using pre-compiled libraries and other resources attached as Git modules
instead of using checkout of SVN repositories in the parent folder.

The directory layout:
```
  * release/datafiles/
    * assets/        -> blender-assets.git
      * publish/
      * ...
      * README.txt
  * lib/
    * darwin_x64/    -> lib-darwin_x64.git
    * darwin_arm64/  -> lib-darwin_arm64.git
    * linux_x64/     -> lib-linux_x64.git
    * windows_x64/   -> lib-windows_x64.git
  * tests/
    * data/         -> blender-test-data.git
```

The changes about configuring the actual Git sub-modules are not included
into this patch, as those require repository to actually exist before it
can be used.

The assets submodule is enabled by default, and the rest of them are
disabled. This means that if someone runs `git submodule update --init`
they will not get heavy libraries. The platform-specific and tests
related submodules are enabled when using `make update` or `make test`.

All the submodules are tracked: this means that when new commits are
done to the submodule, the blender.git repository is to be updated to
point them to the new hash. This causes some extra manual work, but it
allows to more easily update Blender and its dependencies to known good
state when performing operations like bisect.

Ref #108978

Pull Request: https://projects.blender.org/blender/blender/pulls/117946

Co-authored-by: Brecht Van Lommel <brecht@blender.org>
Co-authored-by: Ray Molenkamp <github@lazydodo.com>
Pull Request: https://projects.blender.org/blender/blender/pulls/118628

tests/python/CMakeLists.txt

@@ -6,7 +6,7 @@
 # and don't give deterministic results
 set(USE_EXPERIMENTAL_TESTS FALSE)
 
-set(TEST_SRC_DIR ${CMAKE_SOURCE_DIR}/../lib/tests)
+set(TEST_SRC_DIR ${CMAKE_SOURCE_DIR}/tests/data)
 set(TEST_PYTHON_DIR ${CMAKE_SOURCE_DIR}/tests/python)
 set(TEST_OUT_DIR ${CMAKE_BINARY_DIR}/tests)
 

tests/python/bl_alembic_io_test.py

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 """
-./blender.bin --background -noaudio --factory-startup --python tests/python/bl_alembic_io_test.py -- --testdir /path/to/lib/tests/alembic
+./blender.bin --background -noaudio --factory-startup --python tests/python/bl_alembic_io_test.py -- --testdir /path/to/tests/data/alembic
 """
 
 import math

tests/python/bl_animation_fcurves.py

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 """
-blender -b -noaudio --factory-startup --python tests/python/bl_animation_fcurves.py -- --testdir /path/to/lib/tests/animation
+blender -b -noaudio --factory-startup --python tests/python/bl_animation_fcurves.py -- --testdir /path/to/tests/data/animation
 """
 
 import pathlib

tests/python/bl_constraints.py

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 """
-./blender.bin --background -noaudio --factory-startup --python tests/python/bl_constraints.py -- --testdir /path/to/lib/tests/constraints
+./blender.bin --background -noaudio --factory-startup --python tests/python/bl_constraints.py -- --testdir /path/to/tests/data/constraints
 """
 
 import pathlib

tests/python/bl_rigging_symmetrize.py

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 """
-blender -b -noaudio --factory-startup --python tests/python/bl_rigging_symmetrize.py -- --testdir /path/to/lib/tests/animation
+blender -b -noaudio --factory-startup --python tests/python/bl_rigging_symmetrize.py -- --testdir /path/to/tests/data/animation
 """
 
 import pathlib

tests/python/collada/CMakeLists.txt

@@ -8,7 +8,7 @@
 # and don't give deterministic results
 set(USE_EXPERIMENTAL_TESTS FALSE)
 
-set(TEST_SRC_DIR ${CMAKE_SOURCE_DIR}/../lib/tests)
+set(TEST_SRC_DIR ${CMAKE_SOURCE_DIR}/tests/data)
 set(TEST_OUT_DIR ${CMAKE_BINARY_DIR}/tests)
 
 # ugh, any better way to do this on testing only?

tests/python/collada/animation/test_animation_simple.py

@@ -3,7 +3,7 @@
 
 """
 Call as follows:
-python collada_mesh_simple.py --blender PATH_TO_BLENDER_EXE --testdir PATH_TO_SVN/lib/tests/collada/mesh
+python collada_mesh_simple.py --blender PATH_TO_BLENDER_EXE --testdir tests/data/collada/mesh
 """
 
 import sys

tests/python/collada/mesh/test_mesh_simple.py

@@ -3,7 +3,7 @@
 
 """
 Call as follows:
-python collada_mesh_simple.py --blender PATH_TO_BLENDER_EXE --testdir PATH_TO_SVN/lib/tests/collada/mesh
+python collada_mesh_simple.py --blender PATH_TO_BLENDER_EXE --testdir tests/data/collada/mesh
 """
 
 import sys

tests/python/curve_to_mesh.py

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 # To run all tests, use
-# BLENDER_VERBOSE=1 ./bin/blender ../lib/tests/modeling/curve_to_mesh.blend --python ../blender/tests/python/bl_curve_to_mesh.py -- --run-all-tests
+# BLENDER_VERBOSE=1 ./bin/blender ../tests/data/modeling/curve_to_mesh.blend --python ../blender/tests/python/bl_curve_to_mesh.py -- --run-all-tests
 # (that assumes the test is run from a build directory in the same directory as the source code)
 import bpy
 import os

tests/python/view_layer/CMakeLists.txt

@@ -4,7 +4,7 @@
 
 # Use '--write-blend=/tmp/test.blend' to view output
 
-set(TEST_SRC_DIR ${CMAKE_SOURCE_DIR}/../lib/tests)
+set(TEST_SRC_DIR ${CMAKE_SOURCE_DIR}/tests/data)
 set(TEST_OUT_DIR ${CMAKE_BINARY_DIR}/tests)
 
 # ugh, any better way to do this on testing only?