MDG: enable multiplexed samples

[matthdsm]

Description of feature

Enhance association of sampleinfo with demultiplexed_fastq to enable multiplexed samples, e.g. same sample in multiple libraries.

[matthdsm]

fix groupTuple at https://github.com/nf-cmgg/preprocessing/blob/main/workflows/preprocessing.nf#L188 to merge records on [samplename, library]