Introduce metric aggregation

Added metric aggregation on client side in order to decrease the telemetry server load
Health check (up) and total_block_number now send just the latest value
Floating point gauges now send averages over a time period in seconds - otel_flush_frequency_secs
Counters send the sum of all hits over the timespan
Reduced the frequency of exports - external clients set to 300s

TODO: Address the 0% dht hit rate reported when no block available

availproject / avail-light