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_rpc/base_server_writer.cc b/pw_rpc/base_server_writer.cc
index 4fa1f1f..1e23fc8 100644
--- a/pw_rpc/base_server_writer.cc
+++ b/pw_rpc/base_server_writer.cc
@@ -47,7 +47,7 @@
   state_ = kClosed;
 }
 
-span<std::byte> BaseServerWriter::AcquirePayloadBuffer() {
+std::span<std::byte> BaseServerWriter::AcquirePayloadBuffer() {
   if (!open()) {
     return {};
   }
@@ -56,14 +56,15 @@
   return response_.payload(packet());
 }
 
-Status BaseServerWriter::ReleasePayloadBuffer(span<const std::byte> payload) {
+Status BaseServerWriter::ReleasePayloadBuffer(
+    std::span<const std::byte> payload) {
   if (!open()) {
     return Status::FAILED_PRECONDITION;
   }
   return call_.channel().Send(response_, packet(payload));
 }
 
-Packet BaseServerWriter::packet(span<const std::byte> payload) const {
+Packet BaseServerWriter::packet(std::span<const std::byte> payload) const {
   return Packet(PacketType::RPC,
                 call_.channel().id(),
                 call_.service().id(),