Public Changes -
* Add a pkgconfig installer for `grpcpp_otel_plugin`
Example Changes -
* Add example of how to use the pkgconfig for `grpcpp_otel_plugin` with the existing OpenTelemetry example.
* Add another OpenTelemetry example that uses OTel's OStream exporter. This makes it easier to test the pkgconfig file for `grpcpp_otel_plugin` since the OStream exporter does not require any additional dependencies, as opposed to the Prometheus exporter.
Test changes -
* Modify `run_distrib_test_cmake_pkgconfig.sh` test to install opentelemetry and build the example with the OStream exporter.
Closes#36686
PiperOrigin-RevId: 636965475
Yash Tibrewal