[Feature] add an option to let taxpasta report relative abundance as fractions instead of only counts

[Midnighter]

Is there an existing issue for this?

• [X] I have searched the existing issues

Problem description

See discussion on Slack reported by @AmaliT.

The following config causes errors:

motus_use_relative_abundance:true
motus_save_mgc_read_counts:true

Code sample

             CRITICAL   schema_context      column           check    merge.py:424
                      check_number failure_case index                             
                      0         Column  read_count  dtype('int64')                
                      None      float64  None  

Environment

taxprofiler pipeline

Anything else?

No response