Output sssom mapping files rather than (just) owl

For working with boomer more seemlessly, it would be great if it could output the results as a table:

```
mapping_set_id: https://w3id.org/boomer/s8169763872632786387263
license: https://creativecommons.org/publicdomain/zero/1.0/
curie_map:
UBERON: http...
FMA: http...
```
| subject_id | subject_label | predicate_id | object_id | object_label | confidence | mapping_justification |
| ---------- | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- |
| UBERON:123 | heart | skos:exactMatch | FMA:321 | heart | 0.9 | semapv:UnspecifiedMatching |
| UBERON:123 | soul | skos:exactMatch | FMA:321 | human soul | 0.9 | semapv:UnspecifiedMatching |

Start by locating the code that currently writes OWL output and trace how mapping results are represented before serialization. Compare the requested metadata and table columns with the existing output path; done means boomer can emit the requested SSSOM-style mapping file in addition to OWL, with tests covering the format.

Written by the indexing model from the issue text.