Allow to use AnyInvocable in webrtc. Demonstrate how AnyInvocable can make interface clearer to read and implement Demonstrate that AnyInvocable can reduce binary size Bug: None Change-Id: I33cf33fac6ed3bf4c5e46077d1cd984ca0f253a3 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/267165 Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Reviewed-by: Harald Alvestrand <hta@webrtc.org> Cr-Commit-Position: refs/heads/main@{#37380}