Remove dependency on `wcsnlen` for string length calculation.

The `wcsnlen` function is not consistently available across all target environments. Its prior use was intended as a micro-optimization and safeguard to limit string scanning to the remaining buffer size and prevent potential issues with malformed strings lacking a null terminator.

This change now relies on the implicit `std::wstring_view` constructor to determine the string length. `CopyToEncodedBuffer` will continue to handle truncation effectively, mitigating the original concerns.

PiperOrigin-RevId: 756378282
Change-Id: I858bad01724507f7926f868aa300eabad8a4358c

absl/log/internal/log_message.cc

diff --git a/absl/log/internal/log_message.cc b/absl/log/internal/log_message.cc
index 07d17a0..3aed3a2 100644
--- a/absl/log/internal/log_message.cc
+++ b/absl/log/internal/log_message.cc
@@ -27,7 +27,6 @@
 #include <algorithm>
 #include <array>
 #include <atomic>
-#include <cwchar>
 #include <ios>
 #include <memory>
 #include <ostream>
@@ -425,8 +424,7 @@
     CopyToEncodedBuffer<StringType::kNotLiteral>(
         absl::string_view(kCharNull.data(), kCharNull.size() - 1));
   } else {
-    CopyToEncodedBuffer<StringType::kNotLiteral>(
-        std::wstring_view(v, wcsnlen(v, data_->encoded_remaining().size())));
+    CopyToEncodedBuffer<StringType::kNotLiteral>(v);
   }
   return *this;
 }