Python: gpu module: add new submodules and types

This commit extends the gpu python API with:
```
gpu.types.Buffer         #"__init__", "to_list"
gpu.types.GPUTexture     #"__init__", "clear", "read", "format"
gpu.types.GPUFrameBuffer #"__init__", "bind", "clear", "is_bound", "viewport", ("__enter__",  "__exit__" with "GPUFrameBufferStackContext")
gpu.types.GPUUniformBuf  #"__init__", "update"
gpu.state                #"blend_set",  "blend_get",  "depth_test_set",  "depth_test_get",  "depth_mask_set",  "depth_mask_get",  "viewport_set",  "viewport_get",  "line_width_set",  "line_width_get",  "point_size_set",  "color_mask_set",  "face_culling_set", "front_facing_set",  "program_point_size_set"
```

Add these methods to existing objects:
```
gpu.types.GPUShader  #"uniform_sample", "uniform_buffer"
```

Maniphest Tasks: T80481

Differential Revision: https://developer.blender.org/D8826

source/blender/python/generic/py_capi_utils.c

@@ -282,6 +282,17 @@ int PyC_ParseStringEnum(PyObject *o, void *p)
   return 0;
 }
 
+const char *PyC_StringEnum_FindIDFromValue(const struct PyC_StringEnumItems *items,
+                                           const int value)
+{
+  for (int i = 0; items[i].id; i++) {
+    if (items[i].value == value) {
+      return items[i].id;
+    }
+  }
+  return NULL;
+}
+
 /* silly function, we dont use arg. just check its compatible with __deepcopy__ */
 int PyC_CheckArgs_DeepCopy(PyObject *args)
 {