chore: Move remaining auth methods to plugins (#4900)

* Move Google, Email, and Azure to plugins

* Move OIDC provider, remove old loading code

* Move AuthLogo to plugin

* AuthLogo -> PluginIcon

* Lazy load plugin settings

plugins/email/plugin.json

@@ -0,0 +1,4 @@
+{
+  "name": "Email",
+  "description": "Adds an email magic link authentication provider."
+}