Move nextstrain automation rules and configs to ingest/build-configs

[j23414]

Description of proposed changes

Move automation rules to a "ingest/build-configs/automation" directory. Attempt to follow the template at

https://github.com/nextstrain/pathogen-repo-guide/tree/f825132e441a672586ec1748af4cdb149669f7c3/ingest/build-configs/nextstrain-automation

Related issue(s)

• https://github.com/nextstrain/zika/issues/44

Checklist

• [ ] Checks pass

[j23414]

This is a draft because I'm not confident about the changes here: https://github.com/nextstrain/zika/pull/50/commits/168949e14a8ddf674ee4c223412248d2fc16f4e6