Add name to ActionCable threads
Add name to ActionCable threads

To assist in various debugging scenarios, such as [tracking which types of threads are using db connections][0]

Thread names will now be "ActionCable-worker-N" instead of "worker-N".

This is safe for all ruby versions. In versions which do not have thread names, [concurrent-ruby does not attempt to add the name][1]

In the environment I happened to be testing in:

```ruby
e = Concurrent::ThreadPoolExecutor.new(name: 'ActionCable', min_threads: 2, max_threads: 2)
e.post{sleep 100}
e.post{sleep 100}
Thread.list.map(&:name)
```

[0] https://github.com/puma/puma/issues/1512#issuecomment-756760388
[1] https://github.com/ruby-concurrency/concurrent-ruby/blob/master/lib/concurrent-ruby/concurrent/executor/ruby_thread_pool_executor.rb#L312

joonyou/rails,esparta/rails,rails/rails,bogdanvlviv/rails,MSP-Greg/rails,yahonda/rails,betesh/rails,EmmaB/rails-1,rails/rails,EmmaB/rails-1,yahonda/rails,Envek/rails,MSP-Greg/rails,esparta/rails,Stellenticket/rails,esparta/rails,Vasfed/rails,lcreid/rails,kddeisz/rails,betesh/rails,kddeisz/rails,kmcphillips/rails,georgeclaghorn/rails,Erol/rails,Erol/rails,kddeisz/rails,Stellenticket/rails,Stellenticket/rails,Edouard-chin/rails,Edouard-chin/rails,kmcphillips/rails,lcreid/rails,yawboakye/rails,Vasfed/rails,yawboakye/rails,Erol/rails,kmcphillips/rails,BlakeWilliams/rails,joonyou/rails,Stellenticket/rails,bogdanvlviv/rails,Vasfed/rails,bogdanvlviv/rails,yahonda/rails,MSP-Greg/rails,BlakeWilliams/rails,yawboakye/rails,joonyou/rails,Edouard-chin/rails,lcreid/rails,kddeisz/rails,betesh/rails,georgeclaghorn/rails,Edouard-chin/rails,bogdanvlviv/rails,Envek/rails,joonyou/rails,yawboakye/rails,EmmaB/rails-1,betesh/rails,rails/rails,esparta/rails,Envek/rails,yahonda/rails,Envek/rails,Vasfed/rails,georgeclaghorn/rails,georgeclaghorn/rails,MSP-Greg/rails,Erol/rails,lcreid/rails,BlakeWilliams/rails,kmcphillips/rails,BlakeWilliams/rails,rails/rails