Flaky CI related investigation and fixes

[vigoo]

• Adds the cargo parallel job limit to the cli-tests step too
• Reenables parallel test execution and jUnit reporting
• Updates to the latest test-r which writes out partial jUnit reports after each test (so we get some info even if the CI run times out)
• Adds a timeout to the js-3 worker executor test
• Most importantly moves the epoch tick calls to a separate thread. This is what intrerrupts wasm execution and makes sure the system can yield to other tokio tasks during long-running wasm code. As the tick calls were accidentally also scheduled as tokio tasks, it could not make itself work when the system got overloaded. By moving this to a dedicated separate background thread we no longer have this problem.