A TaskPool is used to execute tasks in the backghround.
Whenever a new sound strip needs their waveform to be computed, it's
added as a task to the TaskPool.
Once the PreviewJob has submitted all available tasks to the task pool,
it waits for all of them to finish before exiting.
The TaskPool is configured to start tasks as soon as they are pushed
onto the task queue.
Authored-by: Lucas Tadeu Teixeira <lucas@lucastadeu.com>
Pull Request: https://projects.blender.org/blender/blender/pulls/108877
b11540a65f