Consider add BTO as a acceptable prefix for anatomical_context_qualifiers along with UBERON and CL

[Qi-ISB]

This request is triggered by the following question related to SIGNOR ingestion:

Question on anatomical_context_qualifiers using columns: CELL_DATA and TISSUE_DATA columns to use for BTO: identifiers?

Reason: SIGNOR didn’t provide a separate mapping file to map BTO to UBERON or CL now. And the total unique number of BTO identifiers in the SIGNOR source file is now 41575, so the issue cannot be solved with a custom dictionary build along the SIGNOR ingestion code & RIG.