Neo.selection.Model: add getController()

Use case are selectionModel based listeners, which should get mapped to view controllers:

{
    module: ComponentTreeList,
    header: {
        text: 'Components'
    },
    selectionModel: {
        listeners: {
            selectionChange: 'onComponentTreeListSelectionChange'
        }
    }
}

this leads to util.Function:

export function resolveCallback(fn, scope=this) {
    if (Neo.isString(fn)) {
        if (!scope[fn] && fn.startsWith('up.')) {
            fn = fn.slice(3);
            while (!scope[fn] && (scope = scope.parent));
        } else {
            scope = scope.getController?.()?.getHandlerScope(fn, null) || scope
        }

        fn = scope[fn]
    }

    return {fn, scope}
}

the SM must try to pass a matching view controller.

@gplanansky