Set up Github Actions for Model Repository

[kaiyiliu-strala]

Set up model repository and relevant github actions for available models provided by the kepler model server. Actions are required for

• continuous training of models for changes to kepler
• to make releases that go hand in hand with kepler releases
• to publish (git push) latest models that are trained in CI

Refer:

• [CI][brainstorming] make model training as a github action based on tekton kepler-model-server#212 (comment)
• [Discussion and action required] ec2 data collection workflows (need links to Kepler) kepler-model-server#258