#22402 set codec to utf-8 so unicode characters display correctly

When unicode characters are used in fields that get displayed in the UI of apps in Maya, they are now correctly displayed as the intended characters rather than incoherent glyphs.
This should probably go in pre_app_init() so that it's in place before any of the apps that launch on startup run (e.g. the File Manager) - pre_app_init() is intended to replace the deprecated init_engine() and runs _after_ PySide has been initialised but replacing init_engine() in the Maya code would also require the _init_pyside() to be replaced with the proper call to _define_qt_base() (which we should also do) and this might exceed the scope of this ticket (it'll definitely need QA'ing)!  So for now, I'd suggest adding pre_app_init() with this code and leave changing init_engine() for another day unless you really want to tidy everything up ;)