[PH2][Sleep] Add an experiment to make Sleep use a NonOwningWaker (grpc#40587)

Closes grpc#40587

COPYBARA_INTEGRATE_REVIEW=grpc#40587 from ac-patel:sleep_experiment 2eb7919
PiperOrigin-RevId: 802437235

Author: ac-patel

bazel/experiments.bzl

@@ -280,6 +280,11 @@
   expiry: 2026/02/01
   owner: akshitpatel@google.com
   test_tags: ["promise_test"]
+- name: sleep_use_non_owning_waker
+  description: If set, the sleep promise uses a non-owning waker.
+  expiry: 2026/02/01
+  owner: akshitpatel@google.com
+  test_tags: ["promise_test"]
 - name: tcp_frame_size_tuning
   description:
     If set, enables TCP to use RPC size estimation made by higher layers.

src/core/lib/experiments/experiments.cc

@@ -90,6 +90,8 @@
   default: true
 - name: sleep_promise_exec_ctx_removal
   default: false
+- name: sleep_use_non_owning_waker
+  default: false
 - name: tcp_frame_size_tuning
   default: false
 - name: tcp_rcv_lowat

src/core/lib/experiments/experiments.h

@@ -56,7 +56,9 @@ Poll<absl::Status> Sleep::operator()() {
 }
 
 Sleep::ActiveClosure::ActiveClosure(Timestamp deadline)
-    : waker_(GetContext<Activity>()->MakeOwningWaker()),
+    : waker_((IsSleepUseNonOwningWakerEnabled())
+                 ? GetContext<Activity>()->MakeNonOwningWaker()
+                 : GetContext<Activity>()->MakeOwningWaker()),
       event_engine_(GetContext<EventEngine>()->shared_from_this()),
       timer_handle_(
           event_engine_->RunAfter(deadline - Timestamp::Now(), this)) {}