Revert "API for periodically regathering ICE candidates"

This reverts commit aa41f0cfa64ece911ae2ecee83fc3190d4a42935.

Reason for revert:
Apparently, use of std::random_device() causes chromium on Linux to fail with this error:
terminating with uncaught exception of type std::__1::system_error: random_device failed to open /dev/urandom: Operation not permitted

Link to bot with failure:
https://build.chromium.org/p/chromium.webrtc.fyi/builders/Linux%20Tester/builds/37563

Original change's description:
> API for periodically regathering ICE candidates
> 
> Adds to the RTCConfiguration `ice_regather_interval_range` which, when
> set, specifies the randomized delay between automatic runs of ICE
> regathering. The regathering will occur on all networks and re-use the
> existing ICE ufrag/password. New connections are established once the
> candidates come back and WebRTC will automatically switch to the new
> connection that corresponds to the currently selected connection.
> 
> Bug: webrtc:7969
> Change-Id: I6bbf5439a48e285f704aed9f408631cba038c82b
> Reviewed-on: https://chromium-review.googlesource.com/562505
> Reviewed-by: Peter Thatcher <pthatcher@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#18978}

TBR=pthatcher@webrtc.org,deadbeef@webrtc.org,steveanton@webrtc.org

No-Try: true
Bug: webrtc:7969
Change-Id: I86ef99e9f1070d3ac265398831317b68f562c614
Reviewed-on: https://chromium-review.googlesource.com/571008
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19024}
diff --git a/webrtc/pc/peerconnection.cc b/webrtc/pc/peerconnection.cc
index 42664b0..a947c30 100644
--- a/webrtc/pc/peerconnection.cc
+++ b/webrtc/pc/peerconnection.cc
@@ -223,20 +223,11 @@
 bool PeerConnectionInterface::RTCConfiguration::operator==(
     const PeerConnectionInterface::RTCConfiguration& o) const {
   // This static_assert prevents us from accidentally breaking operator==.
-  // Note: Order matters! Fields must be ordered the same as RTCConfiguration.
   struct stuff_being_tested_for_equality {
-    IceServers servers;
     IceTransportsType type;
+    IceServers servers;
     BundlePolicy bundle_policy;
     RtcpMuxPolicy rtcp_mux_policy;
-    std::vector<rtc::scoped_refptr<rtc::RTCCertificate>> certificates;
-    int ice_candidate_pool_size;
-    bool disable_ipv6;
-    bool disable_ipv6_on_wifi;
-    bool enable_rtp_data_channel;
-    rtc::Optional<int> screencast_min_bitrate;
-    rtc::Optional<bool> combined_audio_video_bwe;
-    rtc::Optional<bool> enable_dtls_srtp;
     TcpCandidatePolicy tcp_candidate_policy;
     CandidateNetworkPolicy candidate_network_policy;
     int audio_jitter_buffer_max_packets;
@@ -244,15 +235,22 @@
     int ice_connection_receiving_timeout;
     int ice_backup_candidate_pair_ping_interval;
     ContinualGatheringPolicy continual_gathering_policy;
+    std::vector<rtc::scoped_refptr<rtc::RTCCertificate>> certificates;
     bool prioritize_most_likely_ice_candidate_pairs;
     struct cricket::MediaConfig media_config;
+    bool disable_ipv6;
+    bool disable_ipv6_on_wifi;
+    bool enable_rtp_data_channel;
     bool enable_quic;
+    rtc::Optional<int> screencast_min_bitrate;
+    rtc::Optional<bool> combined_audio_video_bwe;
+    rtc::Optional<bool> enable_dtls_srtp;
+    int ice_candidate_pool_size;
     bool prune_turn_ports;
     bool presume_writable_when_fully_relayed;
     bool enable_ice_renomination;
     bool redetermine_role_on_ice_restart;
     rtc::Optional<int> ice_check_min_interval;
-    rtc::Optional<rtc::IntervalRange> ice_regather_interval_range;
   };
   static_assert(sizeof(stuff_being_tested_for_equality) == sizeof(*this),
                 "Did you add something to RTCConfiguration and forget to "
@@ -286,8 +284,7 @@
              o.presume_writable_when_fully_relayed &&
          enable_ice_renomination == o.enable_ice_renomination &&
          redetermine_role_on_ice_restart == o.redetermine_role_on_ice_restart &&
-         ice_check_min_interval == o.ice_check_min_interval &&
-         ice_regather_interval_range == o.ice_regather_interval_range;
+         ice_check_min_interval == o.ice_check_min_interval;
 }
 
 bool PeerConnectionInterface::RTCConfiguration::operator!=(