refactor, validation: Add ChainstateManagerOpts db options

Use ChainstateManagerOpts struct to remove ArgsManager uses from validation.cpp.

This commit does not change behavior.

src/bitcoin-chainstate.cpp

@@ -82,6 +82,7 @@ int main(int argc, char* argv[])
     // SETUP: Chainstate
     const ChainstateManager::Options chainman_opts{
         .chainparams = chainparams,
+        .datadir = gArgs.GetDataDirNet(),
         .adjusted_time_callback = NodeClock::now,
     };
     ChainstateManager chainman{chainman_opts};