feat: migrate CI pipeline to github actions

[tshuli]

This PR migrates the CI pipeline to Github Actions.

Note that we have dropped Sentry integration with this migration to GA.

New environment variables:

• New secrets loaded on github actions.
• Environment secrets: for each environment (staging, staging-alt, release, uat):
  • APP_NAME
  • DEPLOY_ENV
• Repository secrets:
  • AWS_ACCESS_KEY_ID
  • AWS_SECRET_ACCESS_KEY
  • AWS_DEFAULT_REGION
  • ECR_REPO
  • BUCKET_NAME

[karrui]

Lgtm. Just a question; we seem to have 3 of each CI running; I assume that's due to PR CICD steps + staging/staging-alt deployments yeah?

[tshuli]

Just a question; we seem to have 3 of each CI running; I assume that's due to PR CICD steps + staging/staging-alt deployments yeah?
Yup, that is correct.

Closing and reopening to refresh the checks as Travis CI is still there