samples: Bluetooth: central_iso: Desynchronized submission of data

[fgrandel]

Describe the bug

In addition to #70794 (BLE TX buffers should provide for ISO header), there are more bugs in the ISO central sample:

• The sample is not correctly synchronized with the radio clock. Therefore a race condition emerges that ISO sequence numbers will no longer match L2 ISO payload number after a few iterations.
• The sample does not consider rounding errors on nRF boards whose LF clock's period cannot be represented as an integer in microseconds.
• The sample does not take into account that the L2 in the controller systematically skips the second ISO interval (aka payload count/event number) to provide for initial synchronization (i.e. the sequence of events is 1, 3, 4, 5... and not 1, 2, 3, 4)

This is relevant to all nRF platforms that use a 32k sleep clock.

To Reproduce Steps to reproduce the behavior:

• see the behavior described in #70794

Expected behavior With proper synchronization the sample should be able to run for hours without skipping payload numbers even if CONFIG_BT_CTLR_ISOAL_PSN_IGNORE=n.

Impact The sample does not provide a proper template for perfectly synchronized transmission.

Logs and console output see #70794

Environment (please complete the following information): nRF platforms with 32k sleep clock

Additional context I have a fixed sample that I can provide as a PR. Just need some time to make it upstream-ready.

[github-actions[bot]]

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[github-actions[bot]]

This issue has been marked as stale because it has been open (more than) 60 days with no activity. Remove the stale label or add a comment saying that you would like to have the label removed otherwise this issue will automatically be closed in 14 days. Note, that you can always re-open a closed issue at any time.