Make span event reservoir max reservoir size configurable

[vuqtran88]

• Introduces maximumSamplesStored attribute with default value of 1000 for the spanEvents element.
• Introduces the NEW_RELIC_SPAN_EVENTS_MAX_SAMPLES_STORED environment variable.
• Wires up the agent to use the maximumSamplesStored and NEW_RELIC_SPAN_EVENTS_MAX_SAMPLES_STORED.
  1. NEW_RELIC_SPAN_EVENTS_MAX_SAMPLES_STORED will override maximumSamplesStored if set and has value.
  2. Updates the ReporteConfiguration with the new span_events.maximum_samples_stored config like everything else.

  newrelic-dotnet-agent/src/Agent/NewRelic/Agent/Core/Configuration/ReportedConfiguration.cs

  Line 12 in acf267f

  public class ReportedConfiguration

  
  3. Upon sending the Connect request, the agent will use the value from the maximumSamplesStored or NEW_RELIC_SPAN_EVENTS_MAX_SAMPLES_STORED for event_harvest_config.harvest_limit.span_event_data in the Connect payload.
  4. After the agent receives the Connect Service response, it will use the final span reservoir size and report period from the Connect Service replies payload. The field needs to be used in the Connect Service payload for this is

{
    {
         "span_event_harvest_config": {
         "report_period_ms": 60000,
         "harvest_limit": 1000
    }
  ...
}

Refs: https://source.datanerd.us/agents/agent-specs/blob/master/Connect-LEGACY.md#span-event-harvest-config

Acceptance Criterias

• NEW_RELIC_SPAN_EVENTS_MAX_SAMPLES_STORED will override maximumSamplesStored if set and has value.
• Agent will use the span_event_harvest_config setting from Connect Service response.