Cleanup: Move BKE_node.h to C++

See: blender/blender#103343

Changes:
1. Added `BKE_node.hh` file. New file includes old one.
2. Functions moved to new file. Redundant `(void)`, `struct` are removed.
3. All cpp includes replaced from `.h` on `.hh`.
4. Everything in `BKE_node.hh` is on `blender::bke` namespace.
5. All implementation functions moved in namespace.
6. Function names (`BKE_node_*`) changed to `blender::bke::node_*`.
7. `eNodeSizePreset` now is a class, with renamed items.

Pull Request: blender/blender#107790

source/blender/nodes/function/node_function_util.cc

@@ -20,7 +20,7 @@ static bool fn_node_poll_default(const bNodeType * /*ntype*/,
 
 void fn_node_type_base(bNodeType *ntype, int type, const char *name, short nclass)
 {
-  node_type_base(ntype, type, name, nclass);
+  blender::bke::node_type_base(ntype, type, name, nclass);
   ntype->poll = fn_node_poll_default;
   ntype->insert_link = node_insert_link_default;
   ntype->gather_link_search_ops = blender::nodes::search_link_ops_for_basic_node;