Try to start work #4001, would like to start from getting started file: https://github.com/open-telemetry/opentelemetry-python/tree/be02f980f3eb2e43f8afd9c586c4d3c02e7d5906/docs/getting_started

Currently, this folder have 4 examples
flask_example.py
metrics_example.py
otcollector_example.py
tracing_example.py

But the test only have
test_flask.py and test_tracing.py

I think to keep the consistency, we should have the metrics and otcollector in test as well, even though these 2 are pretty easy example.

Not sure if my understanding correct, if it make sense, will open a PR for it.