Make Razor codegen use invariant culture

[pranavkm]

There are places in Razor where we use CultureInfo.CurrentCulture in Razor code generation to format non-user strings. There's no reason to vary generated code based on user culture.

[dougbu]

We may have user-visible problems here. In particular, we have a few places where C# generation uses CurrentCulture when writing out non-string values. Could generate invalid C# if for example an int is negative and the user's culture has a number format with a trailing negative symbol. Should make sure large values (greater than 999), negative values, and so on work end-to-end.

[Eilon]

I think it's extremely unlikely that this would ever be a real issue - I doubt Razor code-gens many negative integers or any fractions. Nevertheless, we should fix for the purpose of correctness.