TraceWriter: should we remove this from templates/samples/examples?

In investigating performance, part of what I was seeing was in `TraceWriter` and allocations down that path. In talking with the team people thought this may even be removed in the current version, so went hunting. Though [`TraceWriter` is obsolete](https://github.com/Azure/azure-webjobs-sdk/blob/dev/src/Microsoft.Azure.WebJobs.Host/TraceWriter.cs#L13), it's still used in almost all of our samples, templates, and a few documentation spots. Should we replace this with `ILogger` everywhere? I'm happy to do a PR if so.

This makes me also question whether or not we should care about optimizations on `TraceWriter*` over in the WebJobs SDK ([issue here](https://github.com/Azure/azure-webjobs-sdk/pull/2794) - specifically, a lock [in `CreateLogger` here](https://github.com/Azure/azure-webjobs-sdk/blob/dev/src/Microsoft.Azure.WebJobs.Host/Bindings/TraceWriter/TraceWriterBinding.cs#L52)) was affecting my load test, of a sample. Though it's deprecated, I wonder if a non-trivial number of users are still using it and it's worth pushing some optimizations for (or, do we fully remove it in vNext to force a move to `ILogger`?)