Fix Cloud Composer Сreate environment operator to validate final env state after creation

[VladaZakharova]

Fix Cloud Composer environment creation to succeed only when the environment is actually usable.

Previously, create could rely on stale state from the create long-running operation, and the AlreadyExists path could incorrectly treat an environment in a bad state as success. This PR makes the create operator verify the current environment state and fail unless it is RUNNING.

The system test retry flow is also updated to delete environments left in ERROR before retrying creation.

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