Bug 1073520 - Optimize render time of panels in settings app

We have some scripts containing logic of multiple panels in a single file, so for some panels we need all sub panels to be loaded at the same time. During the refactoring process such scripts are planned be removed.

I would suggest not to separate the `_loadPanel` function but only remove the `data-require-sub-panels` attribute from the panels that have been refactored, for example, `wifi`, `keyboard`, and `appPermissions`.