reduce task leaking (#2868)

* reduce task leaking

* fix onLeaveContext

sdk/base/lib/util/GetSystemSmtp.ts

@@ -25,10 +25,15 @@ export class GetSystemSmtp {
    * Watches the system SMTP credentials. Returns an async iterator that yields whenever the value changes
    */
   async *watch() {
-    while (true) {
-      let callback: () => void
+    const resolveCell = { resolve: () => {} }
+    this.effects.onLeaveContext(() => {
+      resolveCell.resolve()
+    })
+    while (this.effects.isInContext) {
+      let callback: () => void = () => {}
       const waitForNext = new Promise<void>((resolve) => {
         callback = resolve
+        resolveCell.resolve = resolve
       })
       yield await this.effects.getSystemSmtp({
         callback: () => callback(),