Elevatr

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API Changes
- add argument for specifying temp directory for download files. Allows users to specify a specific location. (Thanks, andrew-caudillo: https://github.com/jhollist/elevatr/issues/95)
- exposed ncpu argument so user can control. Defaults to 2 if more than 2 cores available. Thanks to courtiol for finding this issue and the suggestion!

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Major refactor
- dropped sp, rgdal and rgeos depends
- All sf
- Terra
- Still returns RasterLayer, but raster will be dropped in upcoming release.

Vignette
- Add location clip example
- cleaned up examples (e.g. plot was throwing warning, now max.plot = 1)

Other Changes
- Switched to MIT from CCO
- clean up: typos, update citations for new CRAN req, hide one test (thanks Nowosad)
- Updated documentation

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Startup
- added startup message warning of switch to sf and terra in future releases.

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Fixes
- Changed API ERRORS to messages and return NA. Would bomb out runs when this would happen only occasionally. Also this should meet CRAN policy on failing gracefully.
- Switched long lat check from my homespun thing to st::sf_is_longlat
- Fixed EPQS API URL. Moved to a new one. Thanks haas4726 for the catch.
- URL fixes in docs

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Additions
- OpenTopography now requires an API Key. This can be acquired form OpenTopography. You need to set it with elevatr using elevatr::set_opentopo_key(). After a restart, elevatr will use this key.
- The "Introduction to elevatr" vignette has been updated to include chanage reflected in version 0.4.2 and also includes a new section on accessing data from OpenTopography and details on setting the API key.

Bug Fixes
- The epqs server was occasionally returning an empty response (see https://github.com/jhollist/elevatr/issues/29) and would error. If that happens now, elevatr will retry up to 5 times (which usually fixes the issue). If still an empty response after 5 tries, NA is returned and a warning is issued indicating what happened.
- Changing to future::plans was losing tempfiles on parallel downloads. Moved the change back to serial plan after creation of raster.
- Changed get_tile_xy. My math was messing up in areas near 180/-180 longitude were trying to grab non-existent tiles. Now using slippymath::lonlat_to_tilenum instead.
- NA's introduced with simultaneous gdal mosaic and project. Now uses two steps. Solves https://stackoverflow.com/questions/67839878/gridded-dot-artifacts-in-geom-raster-plot

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Bug Fixes
- Previously errored on solaris. Skipped tests. A fix has been proposed within
sp. Once that is available can re-test on solaris.
- Updated CITATION file to reference new version and new Zenodo DOI