fix(dpg): protocol/convenience method parameters should order by defa…

…ult value

- fix the sequence of parameters not sorted by default value (e.g. optional parameters should be at the end)
- fix a method access privilege
- regen samples & tests

fix Azure#2766

src/AutoRest.CSharp/LowLevel/Output/OperationMethodChainBuilder.cs

@@ -80,7 +80,7 @@ public void BuildNextPageMethod(IReadOnlyDictionary<InputOperation, OperationMet
         public LowLevelClientMethod BuildOperationMethodChain()
         {
             var returnTypeChain = BuildReturnTypes();
-            var protocolMethodParameters = _orderedParameters.Select(p => p.Protocol).WhereNotNull().ToArray();
+            var protocolMethodParameters = _orderedParameters.Select(p => p.Protocol).WhereNotNull().OrderBy(p => p.DefaultValue != null).ToArray();
             var protocolMethodSignature = new MethodSignature(_restClientMethod.Name, _restClientMethod.Summary, _restClientMethod.Description, _restClientMethod.Accessibility | Virtual, returnTypeChain.Protocol, null, protocolMethodParameters);
             var convenienceMethod = ShouldConvenienceMethodGenerated(returnTypeChain) ? BuildConvenienceMethod(returnTypeChain) : null;
 
@@ -173,9 +173,10 @@ private ConvenienceMethod BuildConvenienceMethod(ReturnTypeChain returnTypeChain
                 name = _restClientMethod.Name.IsLastWordSingular() ? $"{_restClientMethod.Name}Value" : $"{_restClientMethod.Name.LastWordToSingular()}Values";
             }
 
-            var parameters = _orderedParameters.Select(p => p.Convenience).WhereNotNull().ToArray();
+            var parameters = _orderedParameters.Select(p => p.Convenience).WhereNotNull().OrderBy(p => p.DefaultValue != null).ToArray();
             var protocolToConvenience = _orderedParameters
                 .Where(p => p.Protocol != null)
+                .OrderBy(p => p.Protocol!.DefaultValue != null)
                 .Select(p => (p.Protocol!, p.Convenience))
                 .ToArray();
 
@@ -184,7 +185,7 @@ private ConvenienceMethod BuildConvenienceMethod(ReturnTypeChain returnTypeChain
             return new ConvenienceMethod(convenienceSignature, protocolToConvenience, returnTypeChain.ConvenienceResponseType, diagnostic);
         }
 
-        public void BuildParameters()
+        private void BuildParameters()
         {
             var operationParameters = Operation.Parameters.Where(rp => !RestClientBuilder.IsIgnoredHeaderParameter(rp));