Sample for new memory model and concurrent collections

[kpgalligan]

Using the nmm PR https://github.com/touchlab/Stately/pull/82

Create a test application that creates concurrent collections (ConcurrentMutableList, etc) and access them from multiple threads. Should be in a sample dir in the repo. Should be built as part of the CI tests. For demonstrating accessing it from multiple threads, you can probably create on the main thread, spawn a coroutine with a new thread Dispatcher, confirm access the collection from there.

[samhill303]

@kpgalligan to add some definition