Region configuration does not work without endpoint override in TimestreamDataSource

[antonliauchuk-tealium]

software.amazon.timestream.jdbc.TimestreamDataSource#getProperties implementation uses region value only if endpoint is not null:
`if (this.endpoint != null) {
if (this.endpoint.isEmpty()) {
final String error = Error.lookup(Error.INVALID_ENDPOINT);
LOGGER.severe(error);
throw new SQLException(error);
}

  if (this.region == null) {
    final String error = Error.lookup(Error.MISSING_SERVICE_REGION);
    LOGGER.severe(error);
    throw new SQLException(error);
  }

  properties.put(TimestreamConnectionProperty.ENDPOINT.getConnectionProperty(), this.endpoint);
  properties.put(TimestreamConnectionProperty.REGION.getConnectionProperty(), this.region);
}`

It's impossible to use endpointDiscovery with region override with current implementation. AmazonTimestreamQueryClient supports region override without endpoint value.