Run lifecycle hooks asynchronously

[christophermaier]

Description

Lifecycle hooks currently run synchronously in the main Supervisor loop. This is Bad(TM), because it leaves open the possibility of a misbehaving hook of one service to block the loop for everyone. When this happens the supervisor will no longer respond to commands or be able to manage any other services until that hook completes.

It would be better to handle this asynchronously.

Acceptance Criteria

• post-run hook no longer blocks
• init hook no longer blocks
• file-updated hook no longer blocks
• health-check hook no longer blocks
• post-run hook no longer blocks
• reconfigure hook no longer blocks
• suitability hook no longer blocks

[christophermaier]

Related to https://github.com/habitat-sh/habitat/issues/1973

[stale[bot]]

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