Bug Report: Column Nullability Not Honored in FlightSqlProducer Schema

### Describe the bug, including details regarding any error messages, version, and platform.

In the FlightSqlProducer class, the getFlightInfoPreparedStatement method is responsible for returning the Arrow Schema of the ResultSet for a given query. However, the returned schema does not accurately reflect the nullability of columns. Regardless of whether a column is defined as nullable or non-nullable, the schema always returns a fixed nullability value.

This leads to incorrect ResultSetMetaData when the schema is consumed via the Flight SQL driver.

Root Cause:

The issue originates in the method:

`org.apache.arrow.driver.jdbc.utils.ConvertUtils.convertArrowFieldsToColumnMetaDataList()`

Here, a list of `org.apache.arrow.vector.types.pojo.Field` objects is converted into `org.apache.calcite.avatica.ColumnMetaData` instances. However, the `setNullable` property of the `ColumnMetaData.Builder` is not being set based on the actual nullability of the Arrow field.

Expected Behavior:

The `setNullable` method of `ColumnMetaData.Builder` should be updated to reflect the value of `field.isNullable()` from the Arrow schema.

Impact:

This bug results in incorrect metadata being exposed to clients using the Flight SQL driver, potentially leading to misinterpretation of the data schema.

Beginnen Sie mit org.apache.arrow.driver.jdbc.utils.ConvertUtils.convertArrowFieldsToColumnMetaDataList(), das Arrow Field-Objekte für den Flight SQL-Treiber in ColumnMetaData-Instanzen umwandelt. Prüfen Sie, wie ColumnMetaData.Builder befüllt wird, und stellen Sie sicher, dass die resultierenden Metadaten die Nullbarkeit jedes Feldes beibehalten. Als erledigt gilt die Aufgabe, wenn nullable und non-nullable Arrow-Felder übereinstimmende ResultSetMetaData-Werte liefern.

Vom Indexierungsmodell aus dem Issue-Text verfasst.