Replace concat fq step with pigz

[georgiesamaha]

Closes #18

• main.nf: Updated the module inclusion for concat_fastqs to use the run_pigz module and removed the parse_required_pycoqc_segments module.
• modules/concat_fq.nf: Removed the concat_fastqs process.
• modules/run_pigz.nf: Added a new concat_fastqs process that uses pigz for concatenating FASTQ files.
• modules/run_nanoplot.nf: Corrected the variable reference for sequencing_summary.fileName.
• nextflow.config: Updated paths for multiqc_config and pycoqc_header_file to use ${projectDir} instead of ${baseDir}. Added configuration for the concat_fastqs process to use pbspro executor with specific resource allocations.