add xml output to bcl2fastq

[matthdsm]

Outputs still seem to miss the RunParameters.xml , but that's because it's not in the test dataset.

cc @delfiterradas,
xref #10117

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Closes #XXX

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[delfiterradas]

Thank you for this @matthdsm!
I have tried the multiqcsav module with these changes but it still doesn't work... However, in the demultiplex pipeline it does, so it might be related to the test dataset :)