[C#] Inconsistent String Comparisons in Schema Field Retrieval Methods

In the Schema class, there are three methods used to retrieve individual fields:

```csharp
public class Schema
{
// ...

public Field GetFieldByName(string name) => FieldsLookup[name].FirstOrDefault();

public int GetFieldIndex(string name, StringComparer comparer)
{
IEqualityComparer equalityComparer = (IEqualityComparer)comparer;
return GetFieldIndex(name, equalityComparer);
}

public int GetFieldIndex(string name, IEqualityComparer comparer = default)
{
// Implementation using the specified comparer
}
}
```

The first method (GetFieldByName) use the default string comparer, while the latter two (GetFieldIndex overloads) are using a culture aware comparator by default (`StringComparer.CurrentCulture`). This inconsistency can be confusing, as it is unclear when custom comparers are utilized.

### Component(s)

C#