Adding stubs to PicardLiftovervcf, GATK4_mergevcfs and filterMutectCalls

[Lucpen]

PR checklist

Closes #XXX

• [x] This comment contains a description of changes (with reason).
• [ ] If you've fixed a bug or added code that should be tested, add tests!
• [ ] If you've added a new tool - have you followed the module conventions in the contribution docs
• [ ] If necessary, include test data in your PR.
• [ ] Remove all TODO statements.
• [x] Emit the versions.yml file.
• [x] Follow the naming conventions.
• [x] Follow the parameters requirements.
• [x] Follow the input/output options guidelines.
• [ ] Add a resource label
• [ ] Use BioConda and BioContainers if possible to fulfil software requirements.
• Ensure that the test works with either Docker / Singularity. Conda CI tests can be quite flaky:
  • [x] PROFILE=docker pytest --tag <MODULE> --symlink --keep-workflow-wd --git-aware
  • [ ] PROFILE=singularity pytest --tag <MODULE> --symlink --keep-workflow-wd --git-aware
  • [ ] PROFILE=conda pytest --tag <MODULE> --symlink --keep-workflow-wd --git-aware

[Lucpen]

There is an error related to Conda that I am unsure on how to fix or if it is necessary to fix it: Caused by: Failed to create Conda environment command: conda create --mkdir --yes --quiet --prefix /home/runner/pytest_workflow_3j9p2vgr/picard_liftovervcf_test_picard_liftovervcf_stubs/work/conda/env-aa7c3f17b3e9b256fbd55d1bfa076bd8 bioconda::picard=2.27.1 status : 1 message: PaddingError: Placeholder of length '80' too short in package /home/runner/pytest_workflow_3j9p2vgr/picard_liftovervcf_test_picard_liftovervcf_stubs/work/conda/env-aa7c3f17b3e9b256fbd55d1bfa076bd8/bin/Rscript. The package must be rebuilt with conda-build > 2.0.

[muffato]

@FriederikeHanssen @ramprasadn . The tests now pass, I think this is good for merging.