Generate well-indented SQL from LogicalPlan

### Is your feature request related to a problem or challenge?

DataFusion provides the capability of "unparsing" a logical plan into SQL via the `unparser` module in the `sql` crate (see https://github.com/apache/datafusion/blob/main/datafusion/sql/src/unparser/plan.rs). [Examples](https://github.com/apache/datafusion/blob/main/datafusion-examples/examples/plan_to_sql.rs) also showcase the `Dialect` features to provide customizable escaping.

As a part of the work on SpiceAI and datafusion-federation, we have some rewrites on the tpch_q13 and we expect the final rewritten SQL to be the following:

```sql
SELECT c_orders.c_count,
Count(1) AS custdist
FROM (SELECT c_custkey AS c_custkey,
"count(tpch.orders.o_orderkey)" AS c_count
FROM (SELECT TPCH.customer.c_custkey,
Count(TPCH.orders.o_orderkey) AS
"COUNT(tpch.orders.o_orderkey)"
FROM TPCH.customer
LEFT JOIN TPCH.orders
ON ( ( TPCH.customer.c_custkey =
TPCH.orders.o_custkey )
AND TPCH.orders.o_comment NOT LIKE
'%special%requests%' )
GROUP BY TPCH.customer.c_custkey)) AS c_orders
GROUP BY c_orders.c_count
ORDER BY custdist DESC NULLS FIRST,
c_orders.c_count DESC NULLS FIRST
```

however the `plan_to_sql` generates a one-line sql which is much harder to read

```sql
SELECT c_orders.c_count, COUNT(1) AS custdist FROM (SELECT c_custkey AS c_custkey, "COUNT(tpch.orders.o_orderkey)" AS c_count FROM (SELECT tpch.customer.c_custkey, COUNT(tpch.orders.o_orderkey) AS "COUNT(tpch.orders.o_orderkey)" FROM tpch.customer LEFT JOIN tpch.orders ON ((tpch.customer.c_custkey = tpch.orders.o_custkey) AND tpch.orders.o_comment NOT LIKE '%special%requests%') GROUP BY tpch.customer.c_custkey)) AS c_orders GROUP BY c_orders.c_count ORDER BY custdist DESC NULLS FIRST, c_orders.c_count DESC NULLS FIRST"
```

### Describe the solution you'd like

I would like to be able to provide an extra parameter to the Unparser, such as `pretty_print` or `indent`, which needs to be respected in the `plan_to_sql`

### Describe alternatives you've considered

Use https://github.com/dprint/dprint on the SQL, but unfortunately SQL is not supported

### Additional context

I used this https://www.dpriver.com/pp/sqlformat.htm to generate the formatted SQL from the SQL generated from dataufusion

Start with datafusion/sql/src/unparser/plan.rs and the datafusion-examples/examples/plan_to_sql.rs example to understand how LogicalPlan is currently converted to one-line SQL. Trace how an extra pretty_print or indent option would reach plan_to_sql, then compare the generated output with the issue's formatted SQL example; done means the option produces readable indentation without losing the existing unparser behavior.

Written by the indexing model from the issue text.