SERVER-50282 adds files into the server repo's buildscripts directory that are intended to be executed on a spawnhost to workaround the fact that evergreen doesn't provide a way to customize spawnhosts on a per project basis.

SERVER-50282 makes a (hopefully) valuable piece of information more accessible, but it's still not a great solution in usability[1] nor maintainability[2]. This ticket is a follow-up to reverse that work in favor of a better solution whenever it becomes possible.

[1] The file still has to be executed by hand, and it lives in a different directory for each spawnhost
[2] Using buildscripts for things that are local to the server repo makes sense (e.g: resmoke or mongosymb). But having items inside buildscripts depend on spawnhost-specific knowledge is a more difficult edge for programmers to remember when they're making a potentially breaking evergreen/evergreen yaml change.