Move che tests to new repo, eclipse-che/che-tests

Move the test related code to the new repo from the `eclipse/che/tests` to `eclipse-che/che-tests`. Related actions that have to be taken (items in bold have higher priority):

• Create a bugzilla ticket to create a new repo DONE
• Move the code
• Setup CI/CD
  • secrets (docker/npm)
  • nightly builds (image)
  • release (productization team?)
    • image
    • npm package
    • git branching/tagging
  • Change current jobs (mainly remove mounting of sources)
    • pr check Che - relatively easy
    • pr check che-theia (extensive logic)
    • pr check che-dashboard
    • ...
  • Create PR check (happy path) in che-tests repo
  • Adapt CRW jobs (should be relatively easy)
    • Mainly the `CodereadyWorkspaces/e2e/basic/typescript-tests`

This issue is related to the issue with QE artifacts handling:

CRW-1576