Mesh: Add "Set Sharpness by Angle" operator

This simple  operator set the edge sharpness attribute on edges,
either extending the existing values or replacing them completely.
It's meant to make it more convenient to manually control the
sharpness now that there can be more reason to do that after
auto smooth became a modifier.

@@ -0,0 +1,94 @@
+/* SPDX-FileCopyrightText: 2024 Blender Authors
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later */
+

@@ -0,0 +34,4 @@
+      CTX_data_scene(C), CTX_data_view_layer(C), CTX_wm_view3d(C));
+
+  for (Object *object : objects) {
+    Mesh &mesh = *static_cast<Mesh *>(object->data);