feat: add isPlugin flag to Server class for plugin identification

Author: bjohansebas

lib/Server.js

@@ -362,6 +362,11 @@ class Server {
      */
 
     this.currentHash = undefined;
+    /**
+     * @private
+     * @type {boolean}
+     */
+    this.isPlugin = false;
   }
 
   static get schema() {
@@ -2345,7 +2350,7 @@ class Server {
           // @ts-expect-error
           this.compiler,
           this.options.devMiddleware,
-          true,
+          this.isPlugin,
         );
       }
 
@@ -3451,6 +3456,7 @@ class Server {
    */
   apply(compiler) {
     this.compiler = compiler;
+    this.isPlugin = true;
     this.logger = this.compiler.getInfrastructureLogger(pluginName);
 
     this.compiler.hooks.watchRun.tapPromise(pluginName, async () => {