STAC query optimizations

[johntruckenbrodt]

This improves the STAC queries in search.STACArchive by

• increasing the timeout and enabling users to modify it (new argument timeout)
• making use of pystac-client's mechanism for retries instead of the own implementation and enabling users to modify it (new argument max_retries)
• significantly increasing the query speed by passing parameters for spatial and temporal querying directly to pystac_client.client.Client.search arguments datetime and bbox instead of to the filter argument