Move XMLBase.xmlify out of class and to a function

This doesn't need to be inherited since it makes no use of other class-owned data or functions. Move it to its own function and fix all callers.

Search the repository for XMLBase.xmlify and every caller. Read the implementation and its call sites first, then move the behavior to a standalone function and update all references. Done means the class-owned method is no longer used and the existing chart-generation behavior remains intact.

Written by the indexing model from the issue text.