Support std::string_view in RTC_LOG macros

Update the logging framework to handle std::string_view as a distinct
type to prevent memory safety issues.

On certain toolchains, such as the Android NDK, std::string_view and
absl::string_view are separate types. Relying on implicit conversions
between them within logging macros can lead to the creation of temporary
objects. Capturing the address of these temporaries results in dangling
pointers, which causes undefined behavior or crashes during logging.

This change introduces a dedicated MakeVal overload for std::string_view
and updates internal type traits to:
* Explicitly support std::string_view when it differs from
  absl::string_view.
* Prevent std::string_view from matching generic stringify or class
  templates that may handle it incorrectly.
* Ensure stable references to string data across different platforms
  and compiler configurations.

Previously, this was implicitly (and not explicitly intentionally) been
handled by the deprecated stringstream MakeVal implementation.

Bug: webrtc:42234461
Change-Id: I1d4fd044837e8ac2b117a12e8da351ce5502953e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/468860
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47602}