Update Github workflows to run unit tests

[pvaneck]

• There is a unit test workflow for gating pull requests.
• Then there is also a workflow that, on each push, runs tests then builds/pushes to docker hub if the tests pass.
• The command was removed from the ModelMeshTearDown test because the test would fail with no such file or directory for command.

Note, tests are not run from the docker build command because of the -DskipTests=true in the mvn command in the Dockerfile. Removing the skipTests flag and running the tests during the image build always fails in the GitHub Actions environment after the tests complete due to connection time outs.

Ex:

[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 49, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] 
[INFO] --- maven-jar-plugin:3.1.2:jar (default-jar) @ model-mesh ---
[INFO] Downloading from central: https://repo.maven.apache.org/maven2/org/apache/maven/maven-archiver/3.4.0/maven-archiver-3.4.0.pom
[INFO] I/O exception (java.net.SocketException) caught when processing request to {s}->https://repo.maven.apache.org:443: Connection timed out (Read failed)
[INFO] Retrying request to {s}->https://repo.maven.apache.org:443
[INFO] I/O exception (java.net.SocketException) caught when processing request to {s}->https://repo.maven.apache.org:443: Connection timed out (Read failed)
[INFO] Retrying request to {s}->https://repo.maven.apache.org:443

I have been unable to figure out why exactly this happens, but it might possibly be due to the amount of time the tests take or some other side effect? Skipping the tests doesn't see this timeout issue.

[chinhuang007]

Should we include pull request merge to trigger this workflow? Not sure it is covered by push.

[chinhuang007]

LGTM!