add nightly coarse amip pipeline

[juliasloan25]

Purpose

closes #965

pipeline tested here: https://buildkite.com/clima/climacoupler-coarse-nightly-amip/builds/19
The runs currently fail due to instability, but are being actively debugged

Content

• add config file for low-res AMIP run
  • copy from config/amip_configs/amip.yml, just change resolution
• add new pipeline
  • use main branches
  • run on clima
  • run 4-6 simulations
• schedule pipeline to run nightly (7pm)
• includes changes from specify sponge in amip config #974

[szy21]

This run will likely fail, but we can still merge it in so that we know whether the coupler runs with the main branch of other repos. I can update the yaml once I find a stable configuration.