[Storage Config] Make db path override related fields private

This part of the config is exposed via the `get_dir_paths` API.

Author: wqfish

config/src/config/storage_config.rs

@@ -29,25 +29,25 @@ pub const BUFFERED_STATE_TARGET_ITEMS_FOR_TEST: usize = 10;
 
 #[derive(Clone, Debug, Default, Deserialize, PartialEq, Eq, Serialize)]
 #[serde(default, deny_unknown_fields)]
-pub struct DbPathConfig {
-    pub ledger_db_path: Option<PathBuf>,
-    pub state_kv_db_path: Option<ShardedDbPathConfig>,
-    pub state_merkle_db_path: Option<ShardedDbPathConfig>,
-    pub hot_state_kv_db_path: Option<ShardedDbPathConfig>,
+struct DbPathConfig {
+    ledger_db_path: Option<PathBuf>,
+    state_kv_db_path: Option<ShardedDbPathConfig>,
+    state_merkle_db_path: Option<ShardedDbPathConfig>,
+    hot_state_kv_db_path: Option<ShardedDbPathConfig>,
 }
 
 #[derive(Clone, Debug, Deserialize, PartialEq, Eq, Serialize)]
 #[serde(deny_unknown_fields)]
-pub struct ShardedDbPathConfig {
-    pub metadata_path: Option<PathBuf>,
-    pub shard_paths: Vec<ShardPathConfig>,
+struct ShardedDbPathConfig {
+    metadata_path: Option<PathBuf>,
+    shard_paths: Vec<ShardPathConfig>,
 }
 
 #[derive(Clone, Debug, Deserialize, PartialEq, Eq, Serialize)]
 #[serde(deny_unknown_fields)]
-pub struct ShardPathConfig {
-    pub shards: String,
-    pub path: PathBuf,
+struct ShardPathConfig {
+    shards: String,
+    path: PathBuf,
 }
 
 impl ShardedDbPathConfig {
@@ -284,7 +284,7 @@ pub struct StorageConfig {
     /// Fine grained control for db paths of individal databases/shards.
     /// If not specificed, will use `dir` as default.
     /// Only allowed when sharding is enabled.
-    pub db_path_overrides: Option<DbPathConfig>,
+    db_path_overrides: Option<DbPathConfig>,
     /// ensure `ulimit -n`, set to 0 to not ensure.
     pub ensure_rlimit_nofile: u64,
     /// panic if failed to ensure `ulimit -n`
@@ -740,10 +740,8 @@ impl ConfigSanitizer for StorageConfig {
 
 #[cfg(test)]
 mod test {
-    use crate::config::{
-        config_optimizer::ConfigOptimizer, NodeConfig, NodeType, PrunerConfig, ShardPathConfig,
-        ShardedDbPathConfig, StorageConfig,
-    };
+    use super::{ShardPathConfig, ShardedDbPathConfig, StorageConfig};
+    use crate::config::{config_optimizer::ConfigOptimizer, NodeConfig, NodeType, PrunerConfig};
     use aptos_types::chain_id::ChainId;
 
     #[test]