kernel: De-globalize fReindex

fReindex is one of the last remaining globals exposed by the kernel
library, so move it into the blockstorage class to reduce the amount of
global mutable state and make the kernel library a bit less awkward to
use.

src/node/blockmanager_args.cpp

@@ -33,6 +33,8 @@ util::Result<void> ApplyArgsManOptions(const ArgsManager& args, BlockManager::Op
 
     if (auto value{args.GetBoolArg("-fastprune")}) opts.fast_prune = *value;
 
+    if (auto value{args.GetBoolArg("-reindex")}) opts.reindex = *value;
+
     return {};
 }
 } // namespace node