refactor: rename some operators and modules.

- rename module OP_MTL_fix_all_material to OP_MTL_fix_all_materials.
- rename operator BBP_OT_fix_all_material to BBP_OT_fix_all_materials.
- rename module UTIL_naming_convension to UTIL_naming_convention.
- change some translation contexts to correspond with this change.

bbp_ng/PROP_preferences.py

@@ -1,6 +1,6 @@
 import bpy
 import os, typing
-from . import UTIL_naming_convension
+from . import UTIL_naming_convention
 
 class RawPreferences():
     cBallanceTextureFolder: typing.ClassVar[str] = ""