refactor: Modularize shamap and nodestore (#5668)

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

include/xrpl/nodestore/DummyScheduler.h

@@ -0,0 +1,45 @@
+//------------------------------------------------------------------------------
+/*
+    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_NODESTORE_DUMMYSCHEDULER_H_INCLUDED
+#define RIPPLE_NODESTORE_DUMMYSCHEDULER_H_INCLUDED
+
+#include <xrpl/nodestore/Scheduler.h>
+
+namespace ripple {
+namespace NodeStore {
+
+/** Simple NodeStore Scheduler that just peforms the tasks synchronously. */
+class DummyScheduler : public Scheduler
+{
+public:
+    DummyScheduler() = default;
+    ~DummyScheduler() = default;
+    void
+    scheduleTask(Task& task) override;
+    void
+    onFetch(FetchReport const& report) override;
+    void
+    onBatchWrite(BatchWriteReport const& report) override;
+};
+
+}  // namespace NodeStore
+}  // namespace ripple
+
+#endif