CSV parsing in `gh [gei|ado2gh|bbs2gh] reclaim-mannequin` rejects valid CSVs

## Description

`gh [gei|ado2gh|bbs2gh] reclaim-mannequin` allows you to pass in a `--csv` of mannequins to reclaim, based on the template generated with `gh [gei|ado2gh|bbs2gh] generate-mannequin-csv`.

At the moment, this only works with CSVs that _exactly_ match the template - for example, if you generate a CSV with the headers quoted (which is allowed in CSV files), it is rejected:

```csv
"mannequin-user","mannequin-id","target-user"
"tim","M_kgDOB65srg","timrogers"
```

This is because, when reading a provided CSV file, we effectively treat the input as text rather than parsing it as a CSV.

It's quite likely that you end up with quoted CSVs, for example if you build them programatically using PowerShell.

We should make the CSV parsing more tolerant.

## Reproduction Steps

1. Call `gh [gei|ado2gh|bbs2gh] reclaim-mannequin --csv`, passing in a CSV like the example above