Reduce duplicate peer traffic for ledger data (#5126)

- Drop duplicate outgoing TMGetLedger messages per peer
  - Allow a retry after 30s in case of peer or network congestion.
  - Addresses RIPD-1870
  - (Changes levelization. That is not desirable, and will need to be fixed.)
- Drop duplicate incoming TMGetLedger messages per peer
  - Allow a retry after 15s in case of peer or network congestion.
  - The requestCookie is ignored when computing the hash, thus increasing
    the chances of detecting duplicate messages.
  - With duplicate messages, keep track of the different requestCookies
    (or lack of cookie). When work is finally done for a given request,
    send the response to all the peers that are waiting on the request,
    sending one message per peer, including all the cookies and
    a "directResponse" flag indicating the data is intended for the
    sender, too.
  - Addresses RIPD-1871
- Drop duplicate incoming TMLedgerData messages
  - Addresses RIPD-1869
- Improve logging related to ledger acquisition
- Class "CanProcess" to keep track of processing of distinct items

---------

Co-authored-by: Valentin Balaschenko <13349202+vlntb@users.noreply.github.com>

src/xrpld/app/misc/HashRouter.cpp

@@ -90,6 +90,20 @@ HashRouter::shouldProcess(
     return s.shouldProcess(suppressionMap_.clock().now(), tx_interval);
 }
 
+bool
+HashRouter::shouldProcessForPeer(
+    uint256 const& key,
+    PeerShortID peer,
+    std::chrono::seconds interval)
+{
+    std::lock_guard lock(mutex_);
+
+    auto& entry = emplace(key).first;
+
+    return entry.shouldProcessForPeer(
+        peer, suppressionMap_.clock().now(), interval);
+}
+
 int
 HashRouter::getFlags(uint256 const& key)
 {
@@ -128,4 +142,13 @@ HashRouter::shouldRelay(uint256 const& key)
     return s.releasePeerSet();
 }
 
+auto
+HashRouter::getPeers(uint256 const& key) -> std::set<PeerShortID>
+{
+    std::lock_guard lock(mutex_);
+
+    auto& s = emplace(key).first;
+    return s.peekPeerSet();
+}
+
 }  // namespace ripple