Merge bitcoin/bitcoin#31519: refactor: Use std::span over Span

ffff4a293a bench: Update span-serialize comment (MarcoFalke)
fa4d6ec97b refactor: Avoid false-positive gcc warning (MarcoFalke)
fa942332b4 scripted-diff: Bump copyright headers after std::span changes (MarcoFalke)
fa0c6b7179 refactor: Remove unused Span alias (MarcoFalke)
fade0b5e5e scripted-diff: Use std::span over Span (MarcoFalke)
fadccc26c0 refactor: Make Span an alias of std::span (MarcoFalke)
fa27e36717 test: Fix broken span_tests (MarcoFalke)
fadf02ef8b refactor: Return std::span from MakeUCharSpan (MarcoFalke)
fa720b94be refactor: Return std::span from MakeByteSpan (MarcoFalke)

Pull request description:

  `Span` has some issues:

  * It does not support fixed-size spans, which are available through `std::span`.
  * It is confusing to have it available and in use at the same time with `std::span`.
  * It does not obey the standard library iterator build hardening flags. See https://github.com/bitcoin/bitcoin/issues/31272 for a discussion. For example, this allows to catch issues like the one fixed in commit fabeca3458.

  Both types are type-safe and can even implicitly convert into each other in most contexts.

  However, exclusively using `std::span` seems less confusing, so do it here with a scripted-diff.

ACKs for top commit:
  l0rinc:
    reACK ffff4a293a
  theuni:
    ACK ffff4a293a.

Tree-SHA512: 9cc2f1f43551e2c07cc09f38b1f27d11e57e9e9bc0c6138c8fddd0cef54b91acd8b14711205ff949be874294a121910d0aceffe0e8914c4cff07f1e0e87ad5b8

src/net_processing.cpp

@@ -1,5 +1,5 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
-// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Copyright (c) 2009-present The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -2281,7 +2281,7 @@ void PeerManagerImpl::ProcessGetBlockData(CNode& pfrom, Peer& peer, const CInv&
             pfrom.fDisconnect = true;
             return;
         }
-        MakeAndPushMessage(pfrom, NetMsgType::BLOCK, Span{block_data});
+        MakeAndPushMessage(pfrom, NetMsgType::BLOCK, std::span{block_data});
         // Don't set pblock as we've sent the block
     } else {
         // Send block from disk