Update Batch2 framework with GATE_WAITING state

[TynerGjs]

Description of Enhancement

• update the batch2 framework to allow handling better handling for gated jobs
• update documentation as required

Acceptance Criteria

• gated job execution uses new state

Solution Design

• Add new work chunk state GATE_WAITING - create gated chunks in this state (see ca.uhn.fhir.batch2.coordinator.JobDataSink#accept) -> update it to set it to GATE_WAITING instead of QUEUED; update the docs
• Change gated step advance in triggerGatedExecutions to transactionally update gated chunks from GATE_WAITING -> READY in a single transaction (update state and update job); database update statement for all chunks in GATE_WAITING for the given job id -> READY