FunctionInvocationContext ILogger missing required scope properties

Related to ILogger / tracewriter plumbing

In script invokers (possibly C# as well):

`protected override async Task InvokeCore(object[] parameters, FunctionInvocationContext context)`

I think `context.Logger` should be scoped to the function so that FileLogger writes to LogFiles/Functions/funcname (https://github.com/Azure/azure-webjobs-sdk-script/blob/core/src/WebJobs.Script/Diagnostics/FileLogger.cs#L57 )

It is missing MS_FunctionName, so the logs are dropped

Start at the script invoker's InvokeCore method and inspect how FunctionInvocationContext.Logger is created or scoped. Read FileLogger.cs at the referenced location to confirm how MS_FunctionName determines the LogFiles/Functions/funcname path. Done means function logs are retained under the expected function-specific directory.

Written by the indexing model from the issue text.