Add csg_manifold.

Revert "Merge pull request godotengine#99959 from fire/vsk-csg-error-and-ctd"

This reverts commit 4b91e98, reversing
changes made to 7bff6c8.

Revert "Add csg boolean operators using elalish/manifold."

This reverts commit fda444b.

Add manifold.

Restore.

modules/csg/SCsub

@@ -6,42 +6,7 @@ Import("env_modules")
 
 env_csg = env_modules.Clone()
 
-env_csg.Append(CPPDEFINES=("MANIFOLD_PAR", "-1"))
-
-# Thirdparty source files
-
-thirdparty_obj = []
-
-thirdparty_dir = "#thirdparty/manifold/"
-thirdparty_sources = [
-    "src/boolean_result.cpp",
-    "src/boolean3.cpp",
-    "src/constructors.cpp",
-    "src/csg_tree.cpp",
-    "src/edge_op.cpp",
-    "src/face_op.cpp",
-    "src/impl.cpp",
-    "src/manifold.cpp",
-    "src/polygon.cpp",
-    "src/properties.cpp",
-    "src/quickhull.cpp",
-    "src/smoothing.cpp",
-    "src/sort.cpp",
-    "src/subdivision.cpp",
-]
-
-thirdparty_sources = [thirdparty_dir + file for file in thirdparty_sources]
-env_csg.Prepend(
-    CPPPATH=[
-        thirdparty_dir + "include",
-    ]
-)
-env_thirdparty = env_csg.Clone()
-env_thirdparty.disable_warnings()
-env_thirdparty.add_source_files(thirdparty_obj, thirdparty_sources)
-env.modules_sources += thirdparty_obj
-
-# Godot's own source files
+# Godot source files
 env_csg.add_source_files(env.modules_sources, "*.cpp")
 if env.editor_build:
     env_csg.add_source_files(env.modules_sources, "editor/*.cpp")