Usage metrics sampler runs with high(er than expected) memory utilization.

[ichekrygin]

In #103 we added the initial support for the CAdvisor Network metrics sampler. As an implementation detail, we leverage advisor container stats as a stats data container:

    // CAdvisor stats.
    // Although, currently, we only collect and report network metrics,
    // we [re]use ContainerStats as a sample value holder since, in the future
    // we may choose to collect addition values (other than Network)
    CAdvisorContainerStats cadvisorv1.ContainerStats

The cadvisorv1.ContainerStats struct is a relatively large (and deep) structure. Since this field is added to a sampleInstance with high(er) cardinality (a slice of samples), we observe the overall memory increase by the sampler process.

[dashpole]

/triage accepted