refactor(plugging,hosting): make plugin content loading synchronous (openscd#787)

* refactor(plugging,hosting): make plugin content loading synchronous

* chore(package): remove carehtml dependency

* refactor(Plugging,Hosting): make plugin content static

* fix(plugging): don't store content to localStorage

* test(open-scd): update snapshot

* fix(nsdoc/Plugging): pass nsdoc object to plugins again

Loading nsdoc from localStorage must not be asynchronous. It therefore can be used as is with the refactored plugin loading mechanism

* refactor(Plugging/Setting): avoid reloading nsdoc on re-render

* docs(plugging): add type annotations and doc links

Co-authored-by: Jakob Vogelsang <[email protected]>

Author: ca-d