Update extras_require for tracing dependencies?

[chriselion]

From the 2.10.4 release notes:

Some additional dependencies are required for the tracing functionality in the execution environment. These can be installed in the base Docker image, or supplied through a conda environment. The relevant packages are
opentelemetry-sdk, opentelemetry-api, opentelemetry-instrumentation, opentelemetry-instrumentation-requests
and depending on your endpoint, either opentelemetry-exporter-otlp or opentelemetry-exporter-zipkin

Would it be possible to add these to the extras_require section of setup.py? That would let a user do something like pip install metaflow[tracing-otel], and it also makes things a lot easier for tools that build lockfiles (for example pip-tools) to understand the transitive dependencies.

If you think this is a worthwhile change, I'll submit a PR.