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>

include/xrpl/proto/ripple.proto

@@ -321,8 +321,18 @@ message TMLedgerData
     required uint32 ledgerSeq       = 2;
     required TMLedgerInfoType type  = 3;
     repeated TMLedgerNode nodes     = 4;
+    // If the peer supports "responseCookies", this field will
+    // never be populated.
     optional uint32 requestCookie   = 5;
     optional TMReplyError error     = 6;
+    // The old field is called "requestCookie", but this is
+    // a response, so this name makes more sense
+    repeated uint32 responseCookies = 7;
+    // If a TMGetLedger request was received without a "requestCookie",
+    // and the peer supports it, this flag will be set to true to
+    // indicate that the receiver should process the result in addition
+    // to forwarding it to its "responseCookies" peers.
+    optional bool directResponse    = 8;
 }
 
 message TMPing