Make constructor public (#80895)

I added extra logging to help us repro Razor formatting bugs, which
included serializing C# options as they're a big cause of issues, and
people can never be relied upon to accurately report what the closure of
them is for a particular document.

Now I have received some logs, and I can't deserialize the options
because there is no parameterless constructor 🤦‍♂️

Author: davidwengier

src/Tools/ExternalAccess/Razor/Features/RazorCSharpSyntaxFormattingOptions.cs

@@ -27,7 +27,7 @@ internal sealed record class RazorCSharpSyntaxFormattingOptions(
     {
         public static readonly RazorCSharpSyntaxFormattingOptions Default = new();
 
-        private RazorCSharpSyntaxFormattingOptions()
+        public RazorCSharpSyntaxFormattingOptions()
             : this(CSharpSyntaxFormattingOptions.Default)
         {
         }