[Feat] Add support for ephemeral workloads

[sleipnir]

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Describe the feature It would be interesting to support a type of actor or actorhost that is ephemeral. Ephemeral in the sense that after executing an action or its lifetime has expired, the pod can be shut down completely.

Why would that be important to you? This is important to support ML loads that are expensive and therefore a long running process may not be the most suitable to use.

Additional context Very important to support better configurations for podTemplate

[sleipnir]

ping @mruoss

[sleipnir]

Closed by https://github.com/eigr/spawn/pull/381