fix [#30623] user-defined render presets bug

this report exposed multiple bugs in blender when using a non utf8 compatible home directory.

- bpy.utils.script_paths() would crash when homedir wasn't utf8 (reported bug)
- PyC_DefaultNameSpace() - would raise an error when running when __file__ was non utf8.
- preset filepath property was not set to accept non utf8.
- bpy.paths.display_name would raise an error on non utf8 paths, (used for preset draw)

release/scripts/modules/bpy/path.py

@@ -118,6 +118,14 @@ def clean_name(name, replace="_"):
     return name
 
 
+def _clean_utf8(name):
+    name = _os.path.splitext(basename(name))[0]
+    if type(name) == bytes:
+        return name.decode("utf8", "replace")
+    else:
+        return name.encode("utf8", "replace").decode("utf8")
+
+
 def display_name(name):
     """
     Creates a display string from name to be used menus and the user interface.
@@ -126,17 +134,18 @@ def display_name(name):
     filenames and module names.
     """
 
-    name_base = _os.path.splitext(name)[0]
+    name = _os.path.splitext(name)[0]
 
     # string replacements
-    name_base = name_base.replace("_colon_", ":")
+    name = name.replace("_colon_", ":")
 
-    name_base = name_base.replace("_", " ")
+    name = name.replace("_", " ")
 
-    if name_base.islower():
-        return name_base.lower().title()
-    else:
-        return name_base
+    if name.islower():
+        name = name.lower().title()
+
+    name = _clean_utf8(name)
+    return name
 
 
 def display_name_from_filepath(name):
@@ -144,11 +153,10 @@ def display_name_from_filepath(name):
     Returns the path stripped of directory and extension,
     ensured to be utf8 compatible.
     """
+
     name = _os.path.splitext(basename(name))[0]
-    if type(name) == bytes:
-        return name.decode("utf8", "replace")
-    else:
-        return name.encode("utf8", "replace").decode("utf8")
+    name = _clean_utf8(name)
+    return name
 
 
 def resolve_ncase(path):