Adopt absl::string_view in function parameters under rtc_base/

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

This CL converts the majority of "const std::string&"s in function
parameters under rtc_base/ to absl::string_view.

Bug: webrtc:13579
Change-Id: I2b1e3776aa42326aa405f76bb324a2d233b21dca
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/254081
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Xavier Lepaul‎ <xalep@webrtc.org>
Reviewed-by: Anders Lilienthal <andersc@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Ali Tofigh <alito@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36239}
diff --git a/rtc_base/ref_counted_object_unittest.cc b/rtc_base/ref_counted_object_unittest.cc
index 6b794e6..ab051d4 100644
--- a/rtc_base/ref_counted_object_unittest.cc
+++ b/rtc_base/ref_counted_object_unittest.cc
@@ -15,6 +15,7 @@
 #include <type_traits>
 #include <utility>
 
+#include "absl/strings/string_view.h"
 #include "api/scoped_refptr.h"
 #include "rtc_base/ref_count.h"
 #include "test/gtest.h"
@@ -52,7 +53,7 @@
 
 class RefClassWithMixedValues : public RefCountInterface {
  public:
-  RefClassWithMixedValues(std::unique_ptr<A> a, int b, const std::string& c)
+  RefClassWithMixedValues(std::unique_ptr<A> a, int b, absl::string_view c)
       : a_(std::move(a)), b_(b), c_(c) {}
 
  protected: