Order Error::Severity enum from most to least severe

- Also reorder Error::Type to match initial values for some consistency

liblangutil/Exceptions.h

@@ -170,6 +170,8 @@ class Error: virtual public util::Exception
 public:
 	enum class Type
 	{
+		Info,
+		Warning,
 		CodeGenerationError,
 		DeclarationError,
 		DocstringParsingError,
@@ -185,15 +187,14 @@ public:
 		UnimplementedFeatureError,
 		YulException,
 		SMTLogicException,
-		Warning,
-		Info
 	};
 
 	enum class Severity
 	{
-		Error,
+		// NOTE: We rely on these being ordered from least to most severe.
+		Info,
 		Warning,
-		Info
+		Error,
 	};
 
 	Error(