Feat/historic telemetry

This feature adds support for historic telemetry recording and querying in-memory for split-proxy. This component accepts a timeslice width (in seconds) and a maximum number of timeslices to keep in memory (the older will be purged as new ones are added).

Now, latencies & status code (which also allow derivation of successful, failed & total requests counts) per endpoint are made available for the last N timeslices. This data will then be feed to the soon to be added observability endpoint.

Data returned by the component (NOT final JSON that will be rendered in the endpoint's response) currently looks like this:

[
   { // timeslice 1
        <resource_a>: {
            status: {
                <code>:  <count>,
                ...
            },
            latency: [<bucket1_count>, ..., <bucket_n_count>]
        },
        <resource_b>: {
            status: {
                <code>:  <count>,
                ...
            },
            latency: [<bucket1_count>, ..., <bucket_n_count>]
        },
    },
    { // timeslice 2
    ...
     }
}

splitio / split-synchronizer

Feat/historic telemetry #177