Change the workflow to run ci tests after a confirmation from the UI

[ahsimb]

This should be similar to how it is done in other repos, for instance in python-extension-common.

• [x] @ahsimb will mark slow tests with @pytest.mark.slow in the context of #119 and #120, resulting in 2 categories of tests:
  • C1) fast tests and
  • C2) slow tests
• [x] @ckunki will update the GitHub workflows to execute
  • the fast tests on each pull_request and
  • the slow ones only if manually confirmed.
• [x] Update Branch protection for Branch main to allow merging only if all tests have been executed and terminated successfully
  • CI / Gate 1 - Regular CI
  • CI / Gate 2 - Allow Merge

[ckunki]

Blocked by issue #120 Add tests with Exasol SaaS / PR #131

[ckunki]

unblocked.