Change default service_name values

[zarirhamza]

Process to change all default values for service_names per integration to DD_SERVICE

• Change default service_name values based on span attribute schema version. If version is v0, the default stays as is, otherwise if it is version v1, the default changes to DD_SERVICE
• Adds and updates all tests for impacted integrations. This includes a new settings_spec.rb per integration that tests the switching of defaults between v0 and v1.
• Encapsulates old peer.service values behind v0 schema version only as there will be changes to the value based on version in the future.

Affected integrations: aws, active_record, active_support, dalli, elasticsearch, ethon, excon, faraday, grpc, http