Add function app dir to worker init request (#8144)

Updated protobuf subtree to tag [v1.5.5-protofile](https://github.com/Azure/azure-functions-language-worker-protobuf/releases/tag/v1.5.5-protofile)

Author: ejizba

src/WebJobs.Script.Grpc/Channel/GrpcWorkerChannel.cs

@@ -228,7 +228,8 @@ internal WorkerInitRequest GetWorkerInitRequest()
             return new WorkerInitRequest()
             {
                 HostVersion = ScriptHost.Version,
-                WorkerDirectory = _workerConfig.Description.WorkerDirectory
+                WorkerDirectory = _workerConfig.Description.WorkerDirectory,
+                FunctionAppDirectory = _applicationHostOptions.CurrentValue.ScriptPath
             };
         }
 

src/WebJobs.Script.Grpc/azure-functions-language-worker-protobuf/src/proto/FunctionRpc.proto

@@ -113,6 +113,9 @@ message WorkerInitRequest {
 
   // Full path of worker.config.json location
   string worker_directory = 4;
+
+  // base directory for function app
+  string function_app_directory = 5;
 }
 
 // Worker responds with the result of initializing itself

test/WebJobs.Script.Tests/Workers/Rpc/GrpcWorkerChannelTests.cs

@@ -225,8 +225,10 @@ public void WorkerInitRequest_Expected()
         {
             WorkerInitRequest initRequest = _workerChannel.GetWorkerInitRequest();
             Assert.NotNull(initRequest.WorkerDirectory);
+            Assert.NotNull(initRequest.FunctionAppDirectory);
             Assert.NotNull(initRequest.HostVersion);
             Assert.Equal("testDir", initRequest.WorkerDirectory);
+            Assert.Equal(_scriptRootPath, initRequest.FunctionAppDirectory);
             Assert.Equal(ScriptHost.Version, initRequest.HostVersion);
         }