Update tile x/y order for ESRI NatGeo World Map tiles

[robe2037]

Tiles for the ESRI NatGeo World Map were being selected and assembled incorrectly.

[robe2037]

I ran into some issues getting tests to pass when checking the package after this change. Issues seem unrelated to the fix made here, but I updated the test suite slightly to resolve the issues.

This involved explicitly defining ext in tests/testthat/setup.R to avoid masking of terra::ext() which was causing sf::st_bbox() to attempt to dispatch on standardGeneric("ext") from terra.

I also explicitly flushed the cache before running the test of the debug client as I was unable to get the client to launch when files were already cached.

With these changes all package checks are now passing on my system.