opentelemetry-cpp v1.16.0 deprecates API methods currently in use

[justin-mccann]

Release v1.16.0 of opentelemetry-cpp includes PR open-telemetry/opentelemetry-cpp#2664, which removes ABI 2 access for several methods.

Two of them are called or mocked in

• exporters/fluentd/test/trace/fluentd_recordable_test.cc
• instrumentation/otel-webserver-module/test/unit/mocks/mock_OpenTelemetry.h

A description of the two batches of relevant changes are at https://github.com/open-telemetry/opentelemetry-cpp/blob/v1.16.0/CHANGELOG.md#1160-2024-06-21