Refactor: Paint: Rename brush _tool properties to _brush_type

This commit renames the python Brush properties that end with `_tool` to
`_brush_type` (e.g. `sculpt_tool` -> `sculpt_brush_type`) to better
distinguish the property from the concept of tools in a workspace
context.

Resolves #124201

Pull Request: https://projects.blender.org/blender/blender/pulls/139909

tests/python/bl_brush_test.py

@@ -60,7 +60,7 @@ class AssetSaveAsTest(unittest.TestCase):
 
         self.assertTrue("Local Copy" in bpy.data.brushes)
         local_brush = bpy.data.brushes["Local Copy"]
-        self.assertEqual(local_brush.sculpt_tool, 'SMOOTH')
+        self.assertEqual(local_brush.sculpt_brush_type, 'SMOOTH')
         self.assertGreaterEqual(local_brush.users, 1)