Break up coverage test into build and test
currently, all other tests are broken into build step and test step so they can be run in parallel and in a pipeline.
but the coverage test https://gitlab.com/autowarefoundation/autoware.auto/AutowareAuto/-/blob/master/tools/coverage/coverage.sh is still a single large build and test job. This has become the bottleneck for the pipeline stage.
Breaking it up into 2 will help make CI run much faster.
Also, coverage test fails randomly frequently, being able to rerun just the testing bit without rebuilding will also speed up execution.