fix(config): Move on-disk txpool elements to data folder (#1287)

Fix for @BrickBera 

<img width="261" alt="image"
src="https://github.com/berachain/polaris/assets/93690142/32f43dff-64a6-4569-aa20-715991ac8ea6">


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Introduced a default value for the transaction journal in the legacy
transaction pool if not provided, enhancing the reliability of the
system.
- **Refactor**
- Updated the configuration structure to use the default legacy
transaction pool configuration, improving code readability and
maintainability.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

cosmos/config/config.go

@@ -279,6 +279,15 @@ func readConfigFromAppOptsParser(parser AppOptionsParser) (*Config, error) {
 		return nil, err
 	}
 
+	if conf.Polar.LegacyTxPool.Journal == "" {
+		conf.Polar.LegacyTxPool.Journal, err =
+			parser.GetString(sdkflags.FlagHome)
+		if err != nil {
+			return nil, err
+		}
+		conf.Polar.LegacyTxPool.Journal += "/data/transactions.rlp"
+	}
+
 	if conf.Polar.LegacyTxPool.Rejournal, err =
 		parser.GetTimeDuration(flags.ReJournal); err != nil {
 		return nil, err

eth/polar/config.go

@@ -51,12 +51,14 @@ func DefaultConfig() *Config {
 	gpoConfig.Default = big.NewInt(gpoDefault)
 	minerCfg := miner.DefaultConfig
 	minerCfg.Etherbase = common.HexToAddress(developmentCoinbase)
-	// TODO: setup proper command line flags
+	legacyPool := legacypool.DefaultConfig
+	legacyPool.Journal = ""
+
 	return &Config{
 		Chain:         *params.DefaultChainConfig,
 		Miner:         minerCfg,
 		GPO:           gpoConfig,
-		LegacyTxPool:  legacypool.DefaultConfig,
+		LegacyTxPool:  legacyPool,
 		RPCGasCap:     ethconfig.Defaults.RPCGasCap,
 		RPCTxFeeCap:   ethconfig.Defaults.RPCTxFeeCap,
 		RPCEVMTimeout: ethconfig.Defaults.RPCEVMTimeout,