Add provisions to specify a database server in testnet manager buildkite

ci/testnet-manager.sh

@@ -64,6 +64,10 @@ EOF
   exit 0
 fi
 
+if [[ -n $TESTNET_DB_HOST ]]; then
+  SOLANA_METRICS_PARTIAL_CONFIG="host=$TESTNET_DB_HOST,$SOLANA_METRICS_PARTIAL_CONFIG"
+fi
+
 export SOLANA_METRICS_CONFIG="db=$TESTNET,$SOLANA_METRICS_PARTIAL_CONFIG"
 echo "SOLANA_METRICS_CONFIG: $SOLANA_METRICS_CONFIG"
 source scripts/configure-metrics.sh