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

app/utils/PluginLoader.ts

@@ -0,0 +1,51 @@
+import React from "react";
+
+interface Plugin {
+  id: string;
+  config: {
+    name: string;
+    description: string;
+    requiredEnvVars?: string[];
+  };
+  settings: React.FC;
+  icon: React.FC<{ size?: number; fill?: string }>;
+}
+
+export default class PluginLoader {
+  private static pluginsCache: { [id: string]: Plugin };
+
+  public static get plugins(): { [id: string]: Plugin } {
+    if (this.pluginsCache) {
+      return this.pluginsCache;
+    }
+    const plugins = {};
+
+    function importAll(r: any, property: string) {
+      Object.keys(r).forEach((key: string) => {
+        const id = key.split("/")[3];
+        plugins[id] = plugins[id] || {
+          id,
+        };
+        plugins[id][property] = r[key].default ?? React.lazy(r[key]);
+      });
+    }
+
+    importAll(
+      import.meta.glob("../../plugins/*/client/Settings.{ts,js,tsx,jsx}"),
+      "settings"
+    );
+    importAll(
+      import.meta.glob("../../plugins/*/client/Icon.{ts,js,tsx,jsx}", {
+        eager: true,
+      }),
+      "icon"
+    );
+    importAll(
+      import.meta.glob("../../plugins/*/plugin.json", { eager: true }),
+      "config"
+    );
+
+    this.pluginsCache = plugins;
+    return plugins;
+  }
+}