Implement OpenTelemetry Instrumentation

[shikokuchuo]

Closes #2421.

This PR implements basic OpenTelemetry instrumentation for knitr.

Abides by general otel semantic conventions in terms of what span names / attributes should look like. As knitr does not fit into any of the existing categories, there are no compulsory attributes to include.

For now, I've included 'engine', 'echo' and 'eval' options as attributes (metadata). Feel free to suggest others to add.

The following is an example screenshot of the spans created (from knitting purrr vignettes). You can see the mirai spans nested within the knitr chunk span.

As per our video call, I've verified that this works fine for python chunks running reticulate.

We cache the otel tracer on package load - if it's not enabled then there is minimal overhead as otel_local_active_span() has an early return if the cached otel_is_tracing variable is FALSE.

Todo:

• Consider other attributes
• Add docs and tests

Feel free to ask any questions / point to other alternatives for implementation that I may not have thought of.

Thanks!

[CLAassistant]

All committers have signed the CLA.

[yihui]

Looks good to me! Just let me know when you think it's ready and I'll merge it. Thanks!

[cderv]

Indeed really clean integration. Thank you!

[shikokuchuo]

I've updated this PR, with the notable changes being:

• Now there are knitr processing and knitr output spans in addition to the chunk spans
  Otel spans are meant to be short-lived, hence we create these to mark the start and end of a knit operation rather than have one span covering the whole thing
• These spans have knitr.format, knitr.input and knitr.output (filename) attributes
• Chunk attributes are now named knitr.chunk.* - with * being device, echo, engine, eval and label
• Added tests

You can see a very small interactive example here (unfortunately it doesn't let me share multiple spans):
https://logfire-eu.pydantic.dev/public-trace/cdd13007-6045-486a-9c08-fb7658f9aa15?spanId=b5e798da01f6b252

I've added a news item, but wasn't sure if you'd want more documentation, or what form that would take. Happy to add something down the line if you let me know what you prefer.

• mirai has this vignette (https://mirai.r-lib.org/articles/v05-opentelemetry.html)
• Shiny is in the process of being released with OpenTelemetry integration so it's blog post will probably also have some good stuff we could borrow from / refer to

[atusy]

How nice! I didn't know there is otel in R.

[yihui]

I'll merge this PR in a second. If you come up with anything else, please feel free to open subsequent PRs. Thanks!