Cycles: Metal host-side code

This patch adds the Metal host-side code:

- Add all core host-side Metal backend files (device_impl, queue, etc)
- Add MetalRT BVH setup files
- Integrate with Cycles device enumeration code
- Revive `path_source_replace_includes` in util/path (required for MSL compilation)

This patch also includes a couple of small kernel-side fixes:

- Add an implementation of `lgammaf` for Metal [Nemes, Gergő (2010), "New asymptotic expansion for the Gamma function", Archiv der Mathematik](https://users.renyi.hu/~gergonemes/)
- include "work_stealing.h" inside the Metal context class because it accesses state now

Ref T92212

Reviewed By: brecht

Maniphest Tasks: T92212

Differential Revision: https://developer.blender.org/D13423

intern/cycles/blender/python.cpp

@@ -906,16 +906,18 @@ static PyObject *enable_print_stats_func(PyObject * /*self*/, PyObject * /*args*
 static PyObject *get_device_types_func(PyObject * /*self*/, PyObject * /*args*/)
 {
   vector<DeviceType> device_types = Device::available_types();
-  bool has_cuda = false, has_optix = false, has_hip = false;
+  bool has_cuda = false, has_optix = false, has_hip = false, has_metal = false;
   foreach (DeviceType device_type, device_types) {
     has_cuda |= (device_type == DEVICE_CUDA);
     has_optix |= (device_type == DEVICE_OPTIX);
     has_hip |= (device_type == DEVICE_HIP);
+    has_metal |= (device_type == DEVICE_METAL);
   }
-  PyObject *list = PyTuple_New(3);
+  PyObject *list = PyTuple_New(4);
   PyTuple_SET_ITEM(list, 0, PyBool_FromLong(has_cuda));
   PyTuple_SET_ITEM(list, 1, PyBool_FromLong(has_optix));
   PyTuple_SET_ITEM(list, 2, PyBool_FromLong(has_hip));
+  PyTuple_SET_ITEM(list, 3, PyBool_FromLong(has_metal));
   return list;
 }
 
@@ -944,6 +946,9 @@ static PyObject *set_device_override_func(PyObject * /*self*/, PyObject *arg)
   else if (override == "HIP") {
     BlenderSession::device_override = DEVICE_MASK_HIP;
   }
+  else if (override == "METAL") {
+    BlenderSession::device_override = DEVICE_MASK_METAL;
+  }
   else {
     printf("\nError: %s is not a valid Cycles device.\n", override.c_str());
     Py_RETURN_FALSE;