Move rtc::NewClosure into own build target as ToQueuedTask

to make it usable without need to depend on rtc_task_queue

Bug: webrtc:10191
Change-Id: I2ae1445cf5d498aa6928d66b6823f2f940987767
Reviewed-on: https://webrtc-review.googlesource.com/c/125084
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26942}
diff --git a/BUILD.gn b/BUILD.gn
index 936c89d..f5b3459 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -492,6 +492,7 @@
       "rtc_base:sigslot_unittest",
       "rtc_base:weak_ptr_unittests",
       "rtc_base/experiments:experiments_unittests",
+      "rtc_base/task_utils:to_queued_task_unittests",
       "sdk:sdk_tests",
       "test/scenario/network:network_emulation_unittests",
     ]