Throw 429's as 429

[DanielLarsenNZ]

@philipf has discovered that 429's are thrown as 500's. It would be good to throw these as 429's and return retry-again-in headers so that clients can back off

Stack trace:
C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.csMicrosoft.Azure.WebJobs.Host, Version=3.0.23.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35: 97)
Inner exception Microsoft.Azure.Cosmos.CosmosException handled at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw:
   at Microsoft.Azure.Cosmos.ResponseMessage.EnsureSuccessStatusCode (Microsoft.Azure.Cosmos.Client, Version=3.14.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
   at Microsoft.Azure.Cosmos.CosmosResponseFactoryCore.ProcessMessage (Microsoft.Azure.Cosmos.Client, Version=3.14.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
   at Microsoft.Azure.Cosmos.CosmosResponseFactoryCore.CreateStoredProcedureExecuteResponse (Microsoft.Azure.Cosmos.Client, Version=3.14.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
   at Microsoft.Azure.Cosmos.Scripts.ScriptsCore+<ExecuteStoredProcedureAsync>d__13`1.MoveNext (Microsoft.Azure.Cosmos.Client, Version=3.14.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)