Work on thread/coroutine scope/schedulers/etc.

Currently we are using threads, coroutine scope, CoroutineDispatcher, and third party library which are also doing the same.

We are not sure that everything is fine, especially the sequencing of the different tasks, which can be an important thing, especially on the crypto module. For the record, the legacy code had two threads managed by the crypto module, one for encrypting and one for decrypting.

Now that we are more experimented with coroutines, let's take time to investigate that and to find a solution that all the team understand and which will work as it's expected to work.

Also some documentation on this subject should be welcome and could be added to the /docs folder as a reference