Merge "Add missing <functional> header for std::function" into main am: 138e470f am: 0ae6956a

Original change: https://android-review.googlesource.com/c/platform/packages/modules/DnsResolver/+/2673540



Change-Id: I78a8b70de6781484a2f320d7957460420f64ec6d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>