Add AES-256-CTR-HMAC-SHA512 Sframe cipher suites

Expose the three AES-256-CTR-HMAC-SHA512 cipher suites from
draft-barnes-sframe-iana-256 (registry values 6, 7 and 8), already
implemented by third_party/sframe, through SframeCipherSuite and map
them in ToSframeCipherSuite. This brings the WebRTC enum in line with
the eight suites listed in the WebRTC Encoded Transform
SFrameCipherSuite IDL, which gained these suites in
https://github.com/w3c/webrtc-encoded-transform/pull/303.

Bug: webrtc:479862368
Change-Id: Ie5f0bbcccfeee9ea7dd69b253c75c8c47082fbc7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/507780
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Kacper Wasniowski <kwasniow@cisco.com>
Cr-Commit-Position: refs/heads/main@{#48822}