Embedder graceful shutdown

[rafaelromcar-parabol]

Issue - Enhancement

Today, when the Embedder receives the SIGTERM signal (for example, when Kubernetes wants to shutdown a pod) it just keeps processing jobs until it receives the SIGKILL and abruptly stops. According to the code, it should just kill itself when it receives the SIGTERM, but it does not act like it.

Proposal:

• Add a message when the Embedder receives the SIGTERM signa.
• Make the Embedder stop pulling new jobs to process.
• Add a message when all jobs are either processed or timed out and the Embedder stops and exists.

Acceptance Criteria (optional)

The Embedder receives the SIGTERM signal and notifies, stops polling jobs from the queue, wait until the jobs it was processing end, and notifies and exists with 0.

Estimated effort: X points (see CONTRIBUTING.md)

[Dschoordsch]

Solved by this PR #9693