Cleanup conda environments

[messersc]

Conda is slow. There is already an option to use mamba instead of conda for solving, but we should further investigate the following fixes:

• [ ] remove defaults channel, as bioconda and conda-forge should be enough.
• [ ] set channel priority to strict (conda config --set channel_priority strict)

Afterwards, evaluate and check if more work is needed here.

[messersc]

tagging @martenj

[messersc]

Alternatively, it looks like it is possible to have one conda environment with all necessary binaries in there and call it with --conda-prefix, cf. https://bioinformatics.stackexchange.com/a/6923