feature: extract async tasks codebase in its own lib

[ClemDoum]

Replaces #1185

Current limitations

As explained in #1185, extensions and other codebases must be able to create, start and potentially monitor tasks. Create tasks from extension will be required in https://github.com/ICIJ/datashare-extension-neo4j as well as in other projects.

Currently, this is not possible.

Solution

@bamthomas suggested to extract task related objects TaskView, TaskManager, TaskSupplier... in their own lib inside this monorepo, the lib will be published in its own jar in order to be imported where relevant. The lib could be named datashare-tasks, datashare-async-tasks...