refactor: Modularize shamap and nodestore (#5668)

This change moves the shamap and nodestore from `xrpld` to `libxrpl`.

include/xrpl/shamap/SHAMapMissingNode.h

@@ -0,0 +1,74 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+    Copyright (c) 2012, 2013 Ripple Labs Inc.
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose  with  or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#ifndef RIPPLE_SHAMAP_SHAMAPMISSINGNODE_H_INCLUDED
+#define RIPPLE_SHAMAP_SHAMAPMISSINGNODE_H_INCLUDED
+
+#include <xrpl/basics/base_uint.h>
+#include <xrpl/shamap/SHAMapTreeNode.h>
+
+#include <iosfwd>
+#include <stdexcept>
+#include <string>
+#include <type_traits>
+
+namespace ripple {
+
+enum class SHAMapType {
+    TRANSACTION = 1,  // A tree of transactions
+    STATE = 2,        // A tree of state nodes
+    FREE = 3,         // A tree not part of a ledger
+};
+
+inline std::string
+to_string(SHAMapType t)
+{
+    switch (t)
+    {
+        case SHAMapType::TRANSACTION:
+            return "Transaction Tree";
+        case SHAMapType::STATE:
+            return "State Tree";
+        case SHAMapType::FREE:
+            return "Free Tree";
+        default:
+            return std::to_string(
+                safe_cast<std::underlying_type_t<SHAMapType>>(t));
+    }
+}
+
+class SHAMapMissingNode : public std::runtime_error
+{
+public:
+    SHAMapMissingNode(SHAMapType t, SHAMapHash const& hash)
+        : std::runtime_error(
+              "Missing Node: " + to_string(t) + ": hash " + to_string(hash))
+    {
+    }
+
+    SHAMapMissingNode(SHAMapType t, uint256 const& id)
+        : std::runtime_error(
+              "Missing Node: " + to_string(t) + ": id " + to_string(id))
+    {
+    }
+};
+
+}  // namespace ripple
+
+#endif