Remove ability for extensions to register a service provider
Remove ability for extensions to register a service provider

The concept of returning a bootstrapper function is simpler and the use of service providers had no advantage over it.

renyuneyun/core,kirkbushell/core,malayladu/core,Albert221/core,Albert221/core,malayladu/core,datitisev/core,Luceos/core,flarum/core,Luceos/core,renyuneyun/core,Albert221/core,renyuneyun/core,kirkbushell/core,malayladu/core,Luceos/core,datitisev/core,Albert221/core,kirkbushell/core,datitisev/core,malayladu/core,kirkbushell/core,flarum/core,datitisev/core,renyuneyun/core,flarum/core,Luceos/core