Split lint & test jobs during ci

[sadlerap]

In primazactl's proposed ci (in #1), we have linting and testing run in the same job. We should split them into two jobs, which carries a few benefits:

• The failure of one doesn't prevent the execution of the other
• Linting and testing don't depend on each other, so we can run them in parallel
• Adding more checks down the line (e.g. security checks) will be easier.