Replace test files with small synthetic ones

• replaces existing larger libraries and annotations in test cases test_create_dag_chart and test_integration_workflow
• adds the following new test files:
  • chr1-10000-20000.fa: artificial chromosome of length 10'000 (based on human chromosome 1)
  • chr1-10000-20000.gtf: matching gene annotation file with two gene and three multi-exon transcripts entries
  • chr1-10000-20000.transcripts.fa: sequences of the transcripts listed in the gene annotation file
  • synthetic.mate_?.fastq.gz: 10 read pairs randomly sampled from the genic regions of the artificial chromosome
  • synthetic.*.bed: BED files with expected alignments for each read; names of overlapping genes are specified in a 7th column
• updates file paths in the relevant sample tables
• extends and updates checksum checking of result files in CI/CD pipeline