Resolve 5818 Update Batch2 framework with GATE_WAITING state

[TynerGjs]

What was done:

• Implemented GATE_WAITING state for the batch2 state machine.
• This will be the initial status for all workchunks of a gated job.
• made compatible with the equivalent "legacy QUEUED" state in the Old batch2 implementation.
• Updated corresponding docs.
• added corresponding tests and changelog

[github-actions[bot]]

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