Add a balanced option for limits.cpu.nodes

[stgraber]

Introduce a new option to limits.cpu.nodes to allow for balancing between NUMA nodes.

This would affect both containers and virtual machines and would basically look at all NUMA nodes on the system on instance startup, pick whichever currently has the lowest usage, store that in a volatile key and then use it as the actual limits.cpu.nodes value within the rest of our logic.

We can refine the logic to identify the least used NUMA node down the line.
Initially we can keep this pretty simple by just mapping out how many instances CPUs are allocated to each node. We'd treat any case where limits.cpu is empty to mean 1 CPU for simplicity.

[stgraber]

Looking into that one now.