Enable psutil CPU Metrics via Configuration or by default

[Satbek]

Description

Add the ability to enable psutil CPU metrics via configuration instead of requiring manual registration in the code.

Context

Currently, CPU metrics that rely on psutil are not available by default. Results can only be obtained for Linux. Reference. These metrics are useful as they provide insights into per-thread CPU load.

However, activating these metrics requires explicit registration of a callback in the code, which is inconvenient.

Expected Behavior

• The ability to enable CPU metrics via configuration instead of requiring manual callback registration.
• Alternatively, have these metrics enabled by default, as they already work correctly on all plafrorms (returns nothing for not linux platform).

Motivation

• Improves usability by reducing the need for manual code changes.
• Ensures CPU metrics are available out of the box for Linux users.

[Satbek]

As an option, psutil-based CPU metrics could be moved to a cpu_extended group and configured like this:

metrics:
  include: [
      cpu_extended
 ]