[keycloak-dev] Removing providers directory

I'm planning on removing the providers directory. Any objections? At the moment we have 3 approaches to deploy custom providers: * 'deployments' dir * 'providers' dir * module The deployments and providers are similar, but deployments is much nicer and more powerful. So we should just remove the providers directory. Modules needs to stay at least for now as that is the only way to deploy custom SPIs.