fix: allow any set query_params to work with query.iter()

[busunkim96]

Construct a ListTimeSeriesRequest from the query params rather than passing them directly to the function. This is important when one of the params is "optional" and is not available as a kwarg on the list_time_series() method.

For example, aggregation must be set on the request object.

Fixes #80

 def list_time_series( self, request: metric_service.ListTimeSeriesRequest = None, *, name: str = None, filter: str = None, interval: common.TimeInterval = None, view: metric_service.ListTimeSeriesRequest.TimeSeriesView = None, retry: retries.Retry = gapic_v1.method.DEFAULT, timeout: float = None, metadata: Sequence[Tuple[str, str]] = (), ) -> pagers.ListTimeSeriesPager:

class ListTimeSeriesRequest(proto.Message): r"""The ``ListTimeSeries`` request.   Attributes:  name (str):  Required. The project on which to execute the request. The  format is:   ::   projects/[PROJECT_ID_OR_NUMBER]  filter (str):  Required. A `monitoring  filter <https://cloud.google.com/monitoring/api/v3/filters>`__  that specifies which time series should be returned. The  filter must specify a single metric type, and can  additionally specify metric labels and other information.  For example:   ::   metric.type = "compute.googleapis.com/instance/cpu/usage_time" AND  metric.labels.instance_name = "my-instance-name".  interval (~.common.TimeInterval):  Required. The time interval for which results  should be returned. Only time series that  contain data points in the specified interval  are included in the response.  aggregation (~.common.Aggregation):  Specifies the alignment of data points in individual time  series as well as how to combine the retrieved time series  across specified labels.   By default (if no ``aggregation`` is explicitly specified),  the raw time series data is returned.  order_by (str):  Unsupported: must be left blank. The points  in each time series are currently returned in  reverse time order (most recent to oldest).  view (~.metric_service.ListTimeSeriesRequest.TimeSeriesView):  Required. Specifies which information is  returned about the time series.  page_size (int):  A positive number that is the maximum number of results to  return. If ``page_size`` is empty or more than 100,000  results, the effective ``page_size`` is 100,000 results. If  ``view`` is set to ``FULL``, this is the maximum number of  ``Points`` returned. If ``view`` is set to ``HEADERS``, this  is the maximum number of ``TimeSeries`` returned.  page_token (str):  If this field is not empty then it must contain the  ``nextPageToken`` value returned by a previous call to this  method. Using this field causes the method to return  additional results from the previous method call.  """