Re-export public symbols in opentelemetry.context

[ngnpope]

Description

Avoids issues with typing where mypy complains because Context is not re-exported when using the following import:

from opentelemetry.context import Context

It's possible to work around this with the following, but it seems as though this is not intended:

from opentelemetry.context.context import Context

Type of change

• Bug fix (non-breaking change which fixes an issue)

Does This PR Require a Contrib Repo Change?

• No.

Checklist:

• Followed the style guidelines of this project

[ngnpope]

@srikanthccv This should also be straightforward - it was one of the typing-related issues I encountered along with the changes in #3285.

[srikanthccv]

It's possible to work around this with the following, but it seems as though this is not intended:

There is already __all__ = ["Context"] in opentelemetry.context.context for this. I think that is intended.

[aabmass]

@srikanthccv this seems to be pretty widely used in the wild, I'm on board with this PR.

[ngnpope]

Thanks @aabmass. I've updated this to (re-)export all public symbols as requested.

The only one I left out was opentelemetry.environment_variables.OTEL_PYTHON_CONTEXT which didn't seem as though it ought to be re-exported and there doesn't seem to be a precedent for that elsewhere.

[aabmass]

LGTM thanks for the PR! @srikanthccv does it look OK to you?

[srikanthccv]

I am fine with this. These transitive imports scare me because you never know how people are using them, and it was an overlooked aspect from our side. Not until metrics SDK we started using private internals and __all__ with specific symbols, so we need to be very cautious about refactoring anything with tracing components.