Add docker-tests coverage of metrics export (#5030)

* Add docker-tests metrics export

* Update dc and otcollector

* Add test_metrics_export_batch_size_two tests http,grpc

* Changelog

* Update tests/opentelemetry-docker-tests/tests/otlpexporter/__init__.py

Co-authored-by: Lukas Hering <40302054+herin049@users.noreply.github.com>

* Update tests/opentelemetry-docker-tests/tests/otlpexporter/__init__.py

Co-authored-by: Lukas Hering <40302054+herin049@users.noreply.github.com>

* Fix import

* Update CHANGELOG.md

* Create 5030.added

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Co-authored-by: Lukas Hering <40302054+herin049@users.noreply.github.com>
Co-authored-by: Leighton Chen <lechen@microsoft.com>
Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>