The startup/shutdown script timeout is not configurable and it's set to 1h

[alexpopero]

Actual behavior

The script timeout for startup/shutdown script is hard-coded to 1h.

Expected Behavior

Both the startup and shutdown script timeouts should be configurable.

Steps to reproduce

Induce a sleep 3601 command in the shutdown script and the instance will hang in terminating:wait, due to Shredder considering the script as failed.

Checklist

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