Add separate semconv page for Apache Dubbo

[steverao]

Fixes #3291

Changes

Add separate semconv page for Apache Dubbo.

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• Links to the prototypes or existing instrumentations (when adding or changing conventions)

[lmolkova]

Looks great! let a few comments - only the error classification on server spans is significant.

[steverao]

@AlbumenJ @chickenlj Please help us to review it together, thanks!

[AlbumenJ]

@oxsean PTAL

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: matt-hensley / name: Matthew Hensley (3ba1702, a7f44b3)
• ✅ login: steverao / name: Steve Rao (3ba1702, a7f44b3, aa2c160)
• ✅ login: trask / name: Trask Stalnaker (3a401e6, 7b6fe84, 85d87f4, 9ac373b)

[lmolkova]

Looks great! Left a non-blocking comment

[steverao]

It seems that everything is fine when I executed following command to run CI locally:

make table-check
make markdown-link-check-local-only

I tried it again but I can't solve them, please tell me how to solve them, thanks!
https://github.com/open-telemetry/semantic-conventions/actions/runs/21938202284/job/63357040415?pr=3292
https://github.com/open-telemetry/semantic-conventions/actions/runs/21938202284/job/63357040449?pr=3292