…casting errors (PowerShell#25396)

# Issue Summary
PowerShell fails to convert numeric strings with thousands separators (e.g., commas) to `[bigint]`, causing casting errors. This occurs because the `ConvertFrom()` method in `LanguagePrimitives.cs` doesn’t handle formatted numbers.

## Cause
- The `ConvertTo()` method doesn’t remove thousands separators (e.g., `,` in en-US), leading to `BigInteger.Parse()` failures.
- This affects scripts handling large numbers with separators.

## Solution
Modify `ConvertFrom()` to:
- Detect the culture-specific thousands separator.
- Remove it before conversion.