Better BIDS TSV reader typing (PR 3)

[MaximeBICMTL]

Builds on #1425 (diff)

Description

Improve the LORIS BIDS reader TSV row typing by typing row data as dict[str, str | None] instead of dict[str, Any]. This loose typing was inherited from the old code, which read and modified the row data directly, which notably caused some bugs such as code using isisntance(row.data['field'], int | float) which is always False since raw tsv data is always a string (or None). The new approach stores the data LORIS is interested in in dedicated fields while the raw data remains unchanged.

Potential follow-ups

1. Replace all tsv n/a values by None on parsing (I think we should do that, it makes the code easier and more intuitive with no real information loss IMO).
2. Accept empty tsv rows (technically incorrect, but might appear in real data and does not hurt IMO, the code currently errors on trailing newlines).