Add run_command abstraction to azure_identity

[arpad-m]

Adds a run_command function to azure_identity and uses it in the one place where we used async-process before. We provide two implementations:

• one based on tokio, behind an optional feature
• the other (used by default) is a manual implementation with a oneshot channel and a dedicated thread

successor of #1654
fixes #1652

[github-actions]

Thank you for your contribution @arpad-m! We will review the pull request and get back to you soon.

[arpad-m]

Note that I have not tested the patch, but the implementation seems pretty straightforward to me.

[heaths]

Thank you for your contribution!

While this does solve the problem, it does not align with our design of providing a means of abstraction to callers e.g., implementing a trait to run on their own async runtime like our HttpClient. That is more what I had in mind when I opened #2002 (more about file IO , but I meant to do async child process forks as well).

We'd certainly be happy to review work more aligned with that. It should go in azure_core in, perhaps, a module named process.