neonvm-daemon: store fractional value in the neonvm-daemon

[mikhail-sakhnov]

We currently never use neonvm-daemon /cpu GET endpoint, since it has no support for fractional CPU limits. Instead we rely on the value stored in the runner memory via atomic variable, which is updated on each scaling request.

As a first step for fractional limits, we might want to move that variable into the neonvm-daemon.

Reasons:

• as said, first step towards proper fractional limits
• clearer ownership - all cpu related state will be kept in a single component (neonvm-daemon) rather than in 2 components as now (neonvm-daemon, neonvm-runner)

Context:
Discussion in #1190 (comment)_

[sharnoff]

This should also be a dependency for #850