balloons: add support for cpu frequency governor tuning

[fmuyassarov]

This commit introduces a new field in the balloons configuration CR, enabling users to specify CPU frequency governor mode preferences.

[fmuyassarov]

@askervin @klihub PTAL. Note that I didn't add a commit for the docs assuming that there might be some changes with the naming or something else. What you guys are happy with the change I will add a commit to update the documentation on this same PR.

[klihub]

LGTM to me. I skimmed through this once, and if I got the naming wrt. config hierarchy right, this looks fine to me.

My only question is that since ATM we can't test this functionality in our e2e test VMs, have you tested this on real HW in practice ?

[fmuyassarov]

LGTM to me. I skimmed through this once, and if I got the naming wrt. config hierarchy right, this looks fine to me.

My only question is that since ATM we can't test this functionality in our e2e test VMs, have you tested this on real HW in practice ?

Yes, I have tested it on my own machine and it works as expected. Fro example, I was checking the updated governor mode of a core belonging to a balloon by simply
cat /sys/devices/system/cpu/cpuN/cpufreq/scaling_governor