[CNVM] Clean snapshots in a graceful shutdown

[amirbenun]

Motivation

Today cloudbeat fails to clean snapshots when context is done, instead we should create a termination context and have the cleanup anyway as part of a graceful shutdown.

Definition of done

• [ ] All created snapshots should be deleted even on a signal

Related tasks/epics

[oren-zohar]

related:

• https://github.com/elastic/cloudbeat/issues/950