Replace targeted coverage report with "alfred qc"

[holtgrewe]

Is your feature request related to a problem? Please describe.
Our targeted coverage quality control currently uses custom scripts that compute minimal coverage per exon rather than average coverage per exon as common.

Describe the solution you'd like
Replace the custom scripts with calling alfred qc and postprocessing the results.

Describe alternatives you've considered
N/A

Additional context

• https://www.gear-genomics.com/alfred/