doc(reference): kernel boot parameters

[MonicaisHer]

This PR adds reference of adding boot parameters to grub.

Parameter checklist:

• [x] nohz
• [x] kthread_cpus
• [x] isolcpus
• [x] domain (as a value for isolcpus)
• [x] timer_migration

optional:

• [x] sched_rt_runtime

PR Preview

[farshidtz]

PR preview link is incorrect. It should be https://canonical-real-time-ubuntu-documentation--13.com.readthedocs.build/en/13/reference/kernel-boot-parameters/