Add overall estimated time remaining to Progressable

[insign]

This PR adds getOverallEstimatedTimeRemaining() to Progressable to bring feature parity with local getEstimatedTimeRemaining(). It calculates the ETA based on the overall progress of all instances. It also updates toArray() to export overall_estimated_time_remaining alongside estimated_time_remaining. Includes time-mocked unit tests for ETA calculation.

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PR created automatically by Jules for task 2713648673096494305 started by @insign

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