Cleanup: use of the term 'len' & 'maxlen'

Only use the term len & maxlen when they represent the length & maximum
length of a string. Instead of the available bytes to use.

Also include the data they're referencing as a suffix, otherwise it's
not always clear what the length is in reference to.

source/blender/python/intern/bpy_interface_run.c

@@ -52,12 +52,12 @@ static void python_script_error_jump_text(Text *text, const char *filepath)
  * Generate a `filepath` from a text-block so we can tell what file a text block comes from.
  */
 static void bpy_text_filepath_get(char *filepath,
-                                  const size_t filepath_maxlen,
+                                  const size_t filepath_maxncpy,
                                   const Main *bmain,
                                   const Text *text)
 {
   BLI_snprintf(filepath,
-               filepath_maxlen,
+               filepath_maxncpy,
                "%s%c%s",
                ID_BLEND_PATH(bmain, &text->id),
                SEP,