reduce repo size (by consolidating test files) #280

this repo has gotten huge and we need to trim some of the fat.

$  du -sch *
2.2G	.git
512	.gitattributes
136K	.github
512	.gitignore
512	.sprocketignore
128K	CONTRIBUTING.md
512	LICENSE.md
128K	README.md
257K	assets
128K	best-practices.md
1.5K	bin
2.0K	conf
258K	data_structures
2.0K	developer_scripts
15K	docker
512	environment.yml
512	requirements-dev.txt
512	requirements.txt
393K	scripts
512	sprocket.toml
130K	template
1.5G	tests
1.9M	tools
1.8M	workflows
3.6G	total

Seems that the largest culprits are tests/ (where we have a bunch of git-lfs stored genomic files) and .git/, which is presumably so large because of the LFS history? I'm not sure exactly how git large-file-storage handles prior versions of files, but we may need to revise and force push some of the history to get rid of all this bloat.

We may eventually want to move our test files out of the git completely, but I don't have a concrete vision for that yet. We could in theory put our genomic test files up in the cloud and pull from blob storage when needed, although that will make our already convoluted CI set up even more messy, so 🤷‍♀️