HttpRuleParser GetExpressionLength allows invalid characters.

[jkotalik]

@Tratcher and I discovered that GetExpressionLength in HttpRuleParser allows invalid characters (including control characters in expressions. GetExpressionLength mentions that we don't really care about the content of a quoted string, however it seems appropriate that if a quoted string has an invalid character, it should throw on parsing here, not in Kestrel (or whatever server).

This would be a breaking change, as it would introduce a new place where an exception is thrown, however it is probably the right behavior.

[aspnet-hello]

This issue was moved to dotnet/aspnetcore#2694