Add more system information as a diagnostics

[IceSentry]

What problem does this solve or what need does it fill?

When debugging performance it can be helpful to know things like cpu usage and memory usage

What solution would you like?

Add a SystemInformationDiagnosticsPlugin to bevy_diagnostics that queries the cpu usage and memory usage and adds them as a diagnostic.

This plugin could also add the SystemInfo from #5454 as a Res to make this data accessible to other parts of the engine.

What alternative(s) have you considered?

None

Additional context

#5454 added a log on startup to give more information about the system, The same crate used in that PR should be used to query this data each frame.

[zeroacez]

Hello!
I have never contributed before but I would like to give this a shot if that is okay with you guys.

[Nilirad]

Try to hear @IceSentry and @l1npengtul first, since they already opened the PRs you see above.

[zeroacez]

I see! #5911 seams to already solve this issue. I will move on to something else then. Thank you.

[elbertronnie]

I guess this issue can be closed now as #5911 has been merged.