Allow renaming worker ThreadPool's thread_name_prefix from worker parameters

[maneesh29s]

The distributed ThreadPoolExecutor sets the name of each thread based on thread_name_prefix parameter.

The dask worker, by default, passes a fixed name Dask-Default-Threads as the thread_name_prefix
Corresponding code in dask worker which sets name

Dask's worker parameters only allow overriding the executor, but since executor has to be an instance of some Executor (i.e. its a python object), we can't pass this object from outside of python,
for example, when passing "worker json spec" to the dask spec command to start a worker.

If we can allow user to override this thread_name_prefix of the default executor, by adding one more parameter in the worker params which accepts a string, that would be useful.

Also on another note, the default name of the worker threadpool, can be derived from the worker's self.name attribute itself, rather than always defaulting to Dask-Default-Threads

[maneesh29s]

I would be happy to raise MR for this. But I would like to know which approach will be better.

1. Add a new parameter to Worker to override threadpool name
2. Use the worker.name to generate the default threadpool name, like {worker.name}-Thread
3. Do both 1 and 2

[jacobtomlinson]

I don't have any strong feelings either way.

Someone else might chime in here later, but I would suggest you move forward with whichever approach would be most helpful to you as a user.