[DOCS] Identify Module functions that only work on specific OS/Distros in the docs

Description
It is confusing in the Modules documentation when a specific module function looks like it is a perfect match for your use case only to find that it only works on specific operating systems. A perfect example of this is https://docs.saltproject.io/en/latest/ref/modules/all/salt.modules.system.html#salt.modules.system.get_reboot_required_witnessed. There is no indication on this page that it would not work across all operating system types. But if you look at the code this has a decorator that limits it to only working on NILRT systems. also described here https://github.com/saltstack/salt/issues/58125#issuecomment-846296346

Suggested Fix
Would it be possible to specify in the documentation when a function is not available on given operating system. I recognize this is not practical to do manually as it could quickly get out of date. I was wondering if there was a way to pull any @depends decorators from the code dynamically and use this in the docs page.

Type of documentation
Salt Modules

Start with the Salt Modules documentation page for salt.modules.system.get_reboot_required_witnessed and the linked discussion in issue #58125. Trace how its @depends decorator is represented in the documentation and assess whether the docs can derive availability automatically. Done means module function documentation identifies operating-system or distribution restrictions without requiring readers to inspect the code.