Refactor log_event_aggregator.rb

[hannahramadan]

Logger was the only logging instrumentation in the agent for awhile. Now that we have Logstasher and Logging, we should refactor the LogEventAggregator class to more cleanly support these three instrumentations.

Example of duplication:

  LOGGER_SUPPORTABILITY_FORMAT = 'Supportability/Logging/Ruby/Logger/%s'.freeze
  LOGSTASHER_SUPPORTABILITY_FORMAT = 'Supportability/Logging/Ruby/LogStasher/%s'.freeze
  LOGGING_SUPPORTABILITY_FORMAT = 'Supportability/Logging/Ruby/Logging/%s'.freeze

comments:
https://github.com/newrelic/newrelic-ruby-agent/pull/3420/changes#r2775307300
https://github.com/newrelic/newrelic-ruby-agent/pull/3420/changes#r2775315348

[Newrelic-Boomi]

https://new-relic.atlassian.net/browse/NR-521428