Create spans instead of TTs

[kford-newrelic]

Description

Replace agent implementation of Transaction Traces with Spans.

Initiative Brief.

Acceptance Criteria

Agent produces spans instead of transaction traces.

Design Consideration/Limitations

N/A

Dependencies

N/A

Additional context

Original Jira Issue - NR-186694
Jira Issue - NR-187780

[workato-integration]

https://new-relic.atlassian.net/browse/NR-187781