Provide useful names for Tasks where possible

[briancroom]

Motivation

In a test process running lots of complex asynchronous code, when things go wrong, it can be difficult to debug the process and understand what each of the Tasks in the process are supposed to be doing.

Proposed solution

To help make this a little easier, whenever the testing library creates a Task for running asynchronous work, it should attempt to specify a name reflecting the task's purpose to aid with debugging.

Potentially interesting info:

• Is it a task spun up for producing the runner plan / evaluating arguments, or for running a test?
• What is the name/identifier of the test that the task for?

[stmontgomery]

Tracked by rdar://160302621