Cleanup using StringComparison.CurrentCulture

We need review using StringComparison.CurrentCulture in all code base.

[Best Practices for Using Strings in .NET](https://docs.microsoft.com/en-us/dotnet/standard/base-types/best-practices-strings)

For stable behavior InvariantCulture looks right for date and time formats but Unicode standard Simple Case Folding is better for comparison and sorting.