Create nf-tests for "fusioncatcher": "detect" and "download" modules

[nschcolnicov]

Description of feature

Create nf-tests for "fusioncatcher" "detect" and "download" modules

[atrigila]

Some notes here:

• The download module tries to download from https://sourceforge.net/projects/fusioncatcher/files/data/. The data is too big for GitPod to handle.
• The detect module needs some of the reference files from the download module.

[atrigila]

Trying to download the files in an HPC resulted in #570

[atrigila]

In principle, FusionCatcher assumes the presence of complete whole-genome genomic and transcriptomic data. One could write nf-tests with a small subset of fastq files but would still need the full fusioncatcher-build reference dataset. These tests may be impractical due to the massive computational/storage requirement.

[rannick]

One could build the references for chr4 or another if necessary.

[atrigila]

Fusioncatcher was migrated to nf-core and stub tests were added: nf-core/modules#8271