Sweep mode does not capture contiguous samples at each tuning step when `num_bytes` > 16KB

What feature would you like to see and why?

When sweep mode is set up with dwell_blocks greater than one, i.e. num_bytes more than 16KB, the firmware captures that many blocks - but not contiguously. It also adds a header to every 16KB block.

This is not that useful, because e.g. an FFT over all the samples captured at each tuning step will not give valid results.

A more useful behaviour would be to capture the number of bytes requested as contiguous samples, and then apply a single header only at the start of that data.

However, since this would differ from previous behaviour (which has always added a per-16KB-block header), we'll need to come up with a way to explicitly request this. A new value of sweep_style might be the way to do that.

Start by tracing firmware sweep mode handling for dwell_blocks, num_bytes, and sweep_style. Review how 16KB block headers are emitted and how a new sweep_style could preserve existing behavior while enabling contiguous samples with one header per tuning step. Done means the requested byte count is contiguous and existing behavior remains available.