Add conda environment file and CI

[backmari]

Resolves: Story 2936: Add GitHub actions to post processing agent

• Add GitHub workflow for a CI pipeline to run on pull requests, new tags and pushes to main. Currently there are two steps: run unit tests and build rpm inside docker. When we have switched to
• Add conda environment.yml used for the unit tests. The environment tries to mimic the packages available on the production environment, rhel7, as closely as possible.
• Clean up the Dockerfile for use in the build rpm step of the CI pipeline