Remove private TimeZoneInfoComparer (dotnet/coreclr#8512)

Remove private TimeZoneInfoComparer (dotnet/coreclr#8512)

Use Comparison<T> instead of IComparer<T> to sort the list of
TimeZoneInfos, which moves the comparison code to the sole place where
it is used, and now that Array.Sort is implemented in terms of
Comparison<T> instead of IComparer<T>, avoids some unnecessary
intermediate allocations.

Commit migrated from https://github.com/dotnet/coreclr/commit/3ff4bd7b39629f6e681d7211dade57369ea586b3