pw_span: Switch from pw::span to std::span

Replace pw::span with std::span and "pw_span/span.h" with <span>
throughout the codebase.

Change-Id: Ib1fa873168b6093794e861611d750fcad6285d6c
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/12801
Commit-Queue: Wyatt Hepler <hepler@google.com>
Reviewed-by: Rob Mohr <mohrr@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
diff --git a/pw_tokenizer/base64.cc b/pw_tokenizer/base64.cc
index e05390e..6ce4a4c 100644
--- a/pw_tokenizer/base64.cc
+++ b/pw_tokenizer/base64.cc
@@ -14,8 +14,9 @@
 
 #include "pw_tokenizer/base64.h"
 
+#include <span>
+
 #include "pw_base64/base64.h"
-#include "pw_span/span.h"
 
 namespace pw::tokenizer {
 
@@ -33,9 +34,9 @@
   char* output = static_cast<char*>(output_buffer);
   output[0] = kBase64Prefix;
 
-  base64::Encode(
-      span(static_cast<const std::byte*>(binary_message), binary_size_bytes),
-      &output[1]);
+  base64::Encode(std::span(static_cast<const std::byte*>(binary_message),
+                           binary_size_bytes),
+                 &output[1]);
 
   return encoded_size;
 }
@@ -52,7 +53,7 @@
 
   return base64::Decode(
       std::string_view(&base64[1], base64_size_bytes - 1),
-      span(static_cast<std::byte*>(output_buffer), output_buffer_size));
+      std::span(static_cast<std::byte*>(output_buffer), output_buffer_size));
 }
 
 }  // namespace pw::tokenizer