Remove inefficient basic file handling pipeline steps

[adamrtalbot]

Description of feature

The following processes do nothing but unpack tars or handle files. We can remove some or all of them to make the pipeline much more efficient:

• ADJUST_MAXBIN2_EXT
• BUSCO_DB_PREPARATION
• BUSCO_SAVE_DOWNLOAD
• CAT_DB_GENERATE
• CAT_DB
• CAT_SUMMARY
• CENTRIFUGE_DB_PREPARATION
• GTDBTK_DB_PREPARATION
• KRAKEN2_DB_PREPARATION
• KRONA_DB
• POOL_PAIRED_READS
• POOL_SINGLE_READS
• RENAME_POSTDASTOOL
• RENAME_PREDASTOOL

All of these steps can be handled with Nextflow. They may require upstream changes in nf-core/modules.

The following processes could be simplified, altered or perhaps removed but will have to be checked on a case-by-case basis:

• CAT
• COMBINE_TSV
• CONVERT_DEPTHS
• QUAST_BINS_SUMMARY
• SPADESHYBRID
• TIARA_CLASSIFY

Related issues:

• https://github.com/nf-core/mag/issues/502
• https://github.com/nf-core/mag/issues/474
• https://github.com/nf-core/mag/issues/462