refactor: Modularize shamap and nodestore (#5668)

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

include/xrpl/shamap/SHAMapLeafNode.h

@@ -0,0 +1,83 @@
+//------------------------------------------------------------------------------
+/*
+    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_SHAMAPLEAFNODE_H_INCLUDED
+#define RIPPLE_SHAMAP_SHAMAPLEAFNODE_H_INCLUDED
+
+#include <xrpl/shamap/SHAMapItem.h>
+#include <xrpl/shamap/SHAMapTreeNode.h>
+
+#include <cstdint>
+
+namespace ripple {
+
+class SHAMapLeafNode : public SHAMapTreeNode
+{
+protected:
+    boost::intrusive_ptr<SHAMapItem const> item_;
+
+    SHAMapLeafNode(
+        boost::intrusive_ptr<SHAMapItem const> item,
+        std::uint32_t cowid);
+
+    SHAMapLeafNode(
+        boost::intrusive_ptr<SHAMapItem const> item,
+        std::uint32_t cowid,
+        SHAMapHash const& hash);
+
+public:
+    SHAMapLeafNode(SHAMapLeafNode const&) = delete;
+    SHAMapLeafNode&
+    operator=(SHAMapLeafNode const&) = delete;
+
+    bool
+    isLeaf() const final override
+    {
+        return true;
+    }
+
+    bool
+    isInner() const final override
+    {
+        return false;
+    }
+
+    void
+    invariants(bool is_root = false) const final override;
+
+public:
+    boost::intrusive_ptr<SHAMapItem const> const&
+    peekItem() const;
+
+    /** Set the item that this node points to and update the node's hash.
+
+        @param i the new item
+        @return false if the change was, effectively, a noop (that is, if the
+                hash was unchanged); true otherwise.
+     */
+    bool
+    setItem(boost::intrusive_ptr<SHAMapItem const> i);
+
+    std::string
+    getString(SHAMapNodeID const&) const final override;
+};
+
+}  // namespace ripple
+
+#endif