preprocess_species downloads too many files

[ethanplunkett]

ebirdst_download() downloads 66 geotiffs for each species - three resolutions each of 22 different datasets.

preprocess_species() should be updated to just download the abundance files (3 datasets) in the resolutions we need (possibly only low res, likely never high res).

For all models start by downloading the low resolution abundance and the spatial metadata and figure out which resolution we are ultimately going to use. Then download the three abundance datasets we use in that resolution.

The spatial metadata is loaded with: ebirdst::load_fac_map_parameters(path = sp_path)

This would speed up fitting of new species and reduce network traffic, especially for the automated CI tests which run frequently.