refactor, txdb: Add CoinsViewOptions struct

Add CoinsViewOptions struct to remove ArgsManager uses from txdb.

To reduce size of this commit, this moves references to gArgs variable out of
txdb.cpp to calling code in validation.cpp. But these moves are temporary. The
gArgs references in validation.cpp are moved out to calling code in init.cpp in
later commits.

This commit does not change behavior.

src/node/coins_view_args.cpp

@@ -0,0 +1,16 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <node/coins_view_args.h>
+
+#include <txdb.h>
+#include <util/system.h>
+
+namespace node {
+void ReadCoinsViewArgs(const ArgsManager& args, CoinsViewOptions& options)
+{
+    if (auto value = args.GetIntArg("-dbbatchsize")) options.batch_write_bytes = *value;
+    if (auto value = args.GetIntArg("-dbcrashratio")) options.simulate_crash_ratio = *value;
+}
+} // namespace node

src/node/coins_view_args.h

@@ -0,0 +1,15 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_NODE_COINS_VIEW_ARGS_H
+#define BITCOIN_NODE_COINS_VIEW_ARGS_H
+
+class ArgsManager;
+struct CoinsViewOptions;
+
+namespace node {
+void ReadCoinsViewArgs(const ArgsManager& args, CoinsViewOptions& options);
+} // namespace node
+
+#endif // BITCOIN_NODE_COINS_VIEW_ARGS_H