java/driver/flight-sql: implement current catalog/current schema via session option

[unikdahal]

What feature or improvement would you like to see?

Follow-up from PR #4444 review.

Go's Flight SQL driver implements current catalog / current schema via session options:

arrow-adbc/go/adbc/driver/flightsql/flightsql_connection.go

Lines 149 to 162 in 60e010c

	// GetCurrentCatalog implements driverbase.CurrentNamespacer.
	func (c *connectionImpl) GetCurrentCatalog() (string, error) {
	options, err := c.getSessionOptions(context.Background())
	if err != nil {
	return "", err
	}
	if catalog, ok := options["catalog"]; ok {
	if val, ok := catalog.(string); ok {
	return val, nil
	}
	return "", c.Base().ErrorHelper.Errorf(adbc.StatusInternal, "server returned non-string catalog %#v", catalog)
	}
	return "", c.Base().ErrorHelper.Errorf(adbc.StatusNotFound, "current catalog not supported")
	}

Java's FlightSqlConnection should do the same instead of leaving them unimplemented.

[unikdahal]

take

[unikdahal]

Depends on #4444. Already implemented and pushed to a local branch will open the PR once #4444 merges.