This moves the construction of StunMessage instances for ConnectionRequest, outside of the Prepare() method. Following this, removing Construct()+Prepare() is relatively straight forward. Bug: none Change-Id: Ibcf0510cef30a6e648005b43602c7ae1fb06729e Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/264558 Reviewed-by: Niels Moller <nisse@webrtc.org> Reviewed-by: Jonas Oreland <jonaso@webrtc.org> Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org> Cr-Commit-Position: refs/heads/main@{#37122}