Adopt absl::string_view in rtc_base/log_sinks

This is part of a large scale effort to increase adoption of
absl::string_view across the WebRTC code base.

This CL adds absl::string_view versions of the OnLogMessage functions in
rtc::LogSink. The const std::string& versions are kept for now since
downstream clients use subclasses of LogSink and need to be migrated
before these are removed.

Bug: webrtc:13579
Change-Id: I57bb72ad503805ff0ca16f1d7aece2d44c65cb73
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/253980
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Xavier Lepaul‎ <xalep@webrtc.org>
Owners-Override: Xavier Lepaul‎ <xalep@webrtc.org>
Commit-Queue: Ali Tofigh <alito@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36189}
diff --git a/rtc_base/logging.h b/rtc_base/logging.h
index 8991f6f..ee4d410 100644
--- a/rtc_base/logging.h
+++ b/rtc_base/logging.h
@@ -112,6 +112,13 @@
                             LoggingSeverity severity);
   virtual void OnLogMessage(const std::string& message) = 0;
 
+  virtual void OnLogMessage(absl::string_view msg,
+                            LoggingSeverity severity,
+                            const char* tag);
+  virtual void OnLogMessage(absl::string_view message,
+                            LoggingSeverity severity);
+  virtual void OnLogMessage(absl::string_view message);
+
  private:
   friend class ::rtc::LogMessage;
 #if RTC_LOG_ENABLED()