Add tests for empty seeds

Describe your changes

Added a tests to look at any seeds that were added and to throw a warning (default behavior) or error (if var error_empty_seeds = true) if any seeds are empty on run end.

new function is part of the tuva project, gets executed on run end with warning, and ci testing is configured to error

How has this been tested?

run locally, ci testing

Reviewer focus

should these be in the tuva project, or only in ci testing?

Checklist before requesting a review

[x] I have added at least one Github label to this PR (bug, enhancement, breaking change,...)
[x] My code follows style guidelines
[ ] (New models) YAML files are categorized by sub folder and models listed in alphabetical order
[ ] (New models) I have added a config to each new model to enable it for claims and/or clinical data
[ ] (New models) I have added the variable tuva_last_run to the final output
[ ] (Optional) I have recorded a Loom to explain this PR

Package release checklist

[ ] I have updated dbt docs
[ ] I have updated the version number in the dbt_project.yml

(Optional) Gif of how this PR makes you feel

(catching errors)

Loom link

https://www.loom.com/share/021325c90ddf43f881df64410df600ee

tuva-health / tuva

Add tests for empty seeds #490