Migrate from deprecated SSLFingerprint::CreateUnique* factories

Instead use shorter SSLFingerprint::Create* names with the same functionality.
Update nearby checks for nullability to more modern practices.
Mark old names deprecated to prevent new usages of it in WebRTC

Bug: None
Change-Id: I558806cd892737a8d0e55192c46d55e798e089c0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/478840
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Auto-Submit: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47909}