refactor, txdb: Use DBParams struct in CBlockTreeDB

Use DBParams 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 chainstate.cpp. But these moves are temporary. The
gArgs references in chainstate.cpp are moved out to calling code in init.cpp in
later commits.

This commit does not change behavior.

src/node/chainstate.cpp

@@ -10,12 +10,14 @@
 #include <consensus/params.h>
 #include <logging.h>
 #include <node/blockstorage.h>
+#include <node/database_args.h>
 #include <node/caches.h>
 #include <sync.h>
 #include <threadsafety.h>
 #include <tinyformat.h>
 #include <txdb.h>
 #include <uint256.h>
+#include <util/system.h>
 #include <util/time.h>
 #include <util/translation.h>
 #include <validation.h>
@@ -64,7 +66,12 @@ ChainstateLoadResult LoadChainstate(ChainstateManager& chainman, const CacheSize
     // new CBlockTreeDB tries to delete the existing file, which
     // fails if it's still open from the previous loop. Close it first:
     pblocktree.reset();
-    pblocktree.reset(new CBlockTreeDB(cache_sizes.block_tree_db, options.block_tree_db_in_memory, options.reindex));
+    pblocktree = std::make_unique<CBlockTreeDB>(DBParams{
+        .path = gArgs.GetDataDirNet() / "blocks" / "index",
+        .cache_bytes = static_cast<size_t>(cache_sizes.block_tree_db),
+        .memory_only = options.block_tree_db_in_memory,
+        .wipe_data = options.reindex,
+        .options = [] { DBOptions options; node::ReadDatabaseArgs(gArgs, options); return options; }()});
 
     if (options.reindex) {
         pblocktree->WriteReindexing(true);