Refactor Github workflows

Currently, we have only the `build_and_test` job which builds, analyzes, tests, and generates packages and some steps are needed only for specific situations like generating packages when a PR is merged. We don't need to generate packages every time a commit is updated. This applies other other steps too. 

Instead of having one job, we should have different jobs for different cases. For example, when a PR is updated building and analyzing is enough, and then when the PR is approved we can run additional tests. Lastly, we would generate packages when the PR is merged.