feat: Add support for harness CI

[calvin-codecov]

Closes https://github.com/codecov/core-engineering/issues/71

• adds CI adapter for harness
• uses env variables from https://developer.harness.io/docs/continuous-integration/troubleshoot-ci/ci-env-var/
• uses CI_ prefixed environment variables variant if available and DRONE_ prefixed environment variables variant if not
• Note: DRONE variables overlap with the Drone CI Adapter as Harness CI is built on top so instead of using eturn os.getenv("DRONE") == "true" for the detect function, using HARNESS_BUILD_ID

Successful Harness CI pipeline build