Update CEUS and WUS grid sources

@allenos A variety of updates are needed to finalize gridded seismicity sources. A variety of people will work on these tasks below. They don't all need to be completed by Oct. 1st but we want to make some significant progress.

• Create polygons for CONUS collection region. A broader area around where we make hazard maps so that gridded seismicity model is reasonably complete at edges.
• Create polygons for sub-regions; we really shouldn't be moving from catalog boundaries based on tectonic region to state and prior model based polygons for catalog properties.
• Consider new attenuation boundary in both of the above.
• Incorporate updated grids; CEUS see #25 (closed); WUS supply to @field and @kmilner_usc.edu
• See https://github.com/usgs/nshmp-haz-catalogs. Decide what to change or add to repo; possibly copy to GitLab.

changed milestone to %Finalize draft NSHM 2023

added 2023 ERF labels

marked the checklist item Create polygons for CONUS collection region. A broader area around where we make hazard maps so that gridded seismicity model is reasonably complete at edges. as completed

marked the checklist item Create polygons for sub-regions; we really shouldn't be moving from catalog boundaries based on tectonic region to state and prior model based polygons for catalog properties. as completed

marked the checklist item Consider new attenuation boundary in both of the above. as completed

marked the checklist item Incorporate updated grids; CEUS see #25 (closed); WUS supply to @field and @kmilner_usc.edu as completed

marked the checklist item See https://github.com/usgs/nshmp-haz-catalogs. Decide what to change or add to repo; possibly copy to GitLab. as completed

Will track catalog organization and versioning separately.
Updated WUS grids resolved in e.g. !70 (merged) and earlier MRs.
Updated CEUS grids in #25 (closed)

closed

• @allenos provided new spatial PDFs spanning a broader region on 6-26-2023.
• These new grids were added for the CEUS in !95 (merged), WUS grids handed off to @kmilner_usc.edu for system processing. See !95 (merged) for plots.
• Updated polygons for the gridded seismicity regions were added in #49 (closed) and !100 (merged)