Testing package clean command

Author: michalChrobot

.yamato/project-tests.yml

@@ -18,6 +18,7 @@ test_{{ project.name }}_{{ platform.name }}_{{ editor }}:
   commands:
     - npm install upm-ci-utils@stable -g --registry https://artifactory.prd.cds.internal.unity3d.com/artifactory/api/npm/upm-npm
     - unity-downloader-cli -u {{ editor }} -c Editor --fast --wait
+    - upm-ci package clean
     - {% if platform.name == "ubuntu" %}DISPLAY=:0 && {% endif %}upm-ci project test -u {{ editor }} --project-path {{ project.path }} --type project-tests --extra-utr-arg="--extra-editor-arg=-testCategory --extra-editor-arg=!Performance --reruncount=1 --clean-library-on-rerun"
   artifacts:
     logs: