[CLI] Add CreateFleet instance info retrieval timeout configurable via DevSettings

[hehe7318]

Description of changes

Exposes the CreateFleet post-launch DescribeInstances retry timeout as a devsetting under DevSettings/Timeouts/ComputeInstanceInfoTimeout (default 90s).

When a compute resource uses CreateFleet (flexible instance types), the node package retries DescribeInstances after launch to tolerate EC2 API eventual consistency. This change lets that timeout be tuned from the cluster config:

DevSettings:
  Timeouts:
    ComputeInstanceInfoTimeout: 90  # seconds

Tests

• Unit tests passed

References

• [Node] Replace IP-based matching with instance-ID-based matching to handle EC2 eventual consistency aws-parallelcluster-node#694

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