Normalize filepaths when parsing patterns from js values (#80511)
## Normalize Windows file paths in pattern construction
When interpreting js_values as `Pattern` objects for interpretation, normalize windows file endings away.
Also enable debug_assertions in unit tests.
### Why?
Enabling debug assertions on CI will prevent us from making mistakes
### Alternates?
Honestly, i am kind of confused about where to put this logic
https://vercel.slack.com/archives/C03EWR7LGEN/p1749854016509599?thread_ts=1749833045.978729&cid=C03EWR7LGEN
`Pattern::normalize` and `Pattern::with_normalized_path` are both reasonable alternatives. However, the fact that `normalize` doesn't call `with_normalized_path` was a bit concerning, as was the complex nature of the Pattern type.
Fixes PACK-3279
Part of PACK-4578