(fix)O3-5322: submit orders in parallel

[BlessedAmrita]

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Summary

This PR updates the order basket submission logic to submit multiple orders concurrently instead of sequentially.

Previously, postOrders awaited each individual order submission inside a loop, causing requests to be sent one after another. This was mentioned in the discussion of PR #2920. Following that discussion, this change refactors the logic to submit all orders in parallel while still collecting per-order success and error results.

The existing behavior and return structure are preserved by using Promise.allSettled, ensuring partial failures do not block other order submissions.

Screenshots

Related Issue

https://issues.openmrs.org/browse/O3-5322

Other