Make a few more members const, remove members that aren't used, set max ssl version number on construction and remove setter. Bug: none Change-Id: I6c1a7cabf1e795e027f1bc53b994517e9aef0e93 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/213780 Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Commit-Queue: Tommi <tommi@webrtc.org> Cr-Commit-Position: refs/heads/master@{#33622}