chore: move tracing-opentelemetry from the master branch

[davidbarsky]

This PR removes tracing-opentelemetry to a dedicated repo located at https://github.com/tokio-rs/tracing-opentelemetry. (Note that at time of writing this PR, the new repo has not be made public). We're moving tracing-opentelemetry to a dedicated repository for the following reasons:

1. opentelemetry's MSRV is higher than that of tracing's.
2. more importantly, the main tracing repo is getting a bit unweildy and it feels unreasonable to maintain backports for crates that integrate with the larger tracing ecosystem.

(https://github.com/tokio-rs/tracing-opentelemetry does not have the examples present in this repo; this will occur in a PR that will be linked from this PR.)

[punkeel]

I understand you didn't migrate the examples yet. I believe if you remove the tracing_opentelemetry dependency from examples/Cargo.toml, you should also remove the following example files (otherwise tests will fail):

• examples/examples/opentelemetry.rs
• examples/examples/opentelemetry-remote-context.rs

and remove the mentions from examples/README.md

[davidbarsky]

I understand you didn't migrate the examples yet. I believe if you remove the tracing_opentelemetry dependency from examples/Cargo.toml, you should also remove the following example files (otherwise tests will fail):

Yup, I meant to say that I'd be relying on CI to catch this, but was too tired and forgot. Those will be moved over to the new repo.

[hawkw]

The clippy failure is due to a new warning in unrelated code; I think we should ignore that failure when merging this PR and fix the warning separately. However, I think the examples need to be updated so that cargo test jobs will pass.

Also, I think there are some docs references in tracing and in the main repo-level README that ought to be updated to point at tracing-opentelemetry's new location. We could do that as part of this branch, or in a separate one...I don't have a strong opinion either way, as long as we make sure it happens.

I'll admin merge this once the test failures are addressed, so that we can fix the clippy failure separately.

[davidbarsky]

I'll update the docs and example to point to the new repo. Do you mind making the new repo public in the meantime?

[hawkw]

Do you mind making the new repo public in the meantime?

@davidbarsky done, I was gonna do it once the code was moved over but then I forgot, whoops. BTW, you also have the admin bit for that repo.

[hawkw]

@davidbarsky any updates on changing/removing the examples? I'd really like to get this merged.

[davidbarsky]

netlify is failing due to:

6:10:24 PM: Failed during stage 'preparing repo': error checking for ref: : fatal: unable to access 'https://github.com/tokio-rs/tracing/': Failed to connect to github.com port 443: Connection refused

I'm sure it'll be fixed soon. I'll fix clippy here as well.

[hawkw]

you love to see it!