verify epp/bbr do not have cross imports

[nirrozenbaum]

today bbr imports epp in some of the files.
inspired by the verify-framework-imports, we should create a small program that can run to verify bbr doesn't import epp (and epp doesn't import bbr).
we should allow being strict (fail the script) or just output the violations.

we should then use the output of this script to fix imports and make sure bbr/epp are completely separate.
common code might be extracted to a common package that the two components use.

after it works we can also integrate it in the CI pipeline to make sure incoming PRs don't break this.

[asaadbalum]

/assign