Instead of querying the slots in the shadow DOM after the first render
just add all available slots to the light DOM.

This fixes missing filled slots when slots where added after the first render,
for example if they were used only after some property is set.

This makes problems with the new scoped elements polyfill, which now correctly
makes globally registered elements not visible in the shadow roots. Instead
we have to add the tempaltes at the level of the templates so they get their
global web components and only then transplant them into the light dom of the
nested web components with their own registries.

Allow globally overriding slots in the light dom of components and use it to override the auth-info slot in the Nextcloud file picker

We should try to avoid changing the DOM directly and these helpers go against that.
They both just add two lines of code which we can just copy around if needed.