feat: add new Opik Tracer (#6928)

* feat: add new Opik Tracer

This PR adds a new Tracer to sends traces and spans to Opik.

* Fix typo in docs

* Optimize Opik integration to reduce number of HTTP calls

* Add session_id and user_id to the Opik tracer

* Check Opik configuration on the client side before making a remote check

* Tackle documentation reviews

* Apply suggestions from code review

Co-authored-by: Jacques Verré <jverre@gmail.com>

* Fix one of the doc link

* Explicitely check for Opik environment variables before enabling the Opik tracer

* test: add opik tracing unit tests

---------

Co-authored-by: Nadir J <31660040+NadirJ@users.noreply.github.com>
Co-authored-by: Jacques Verré <jverre@gmail.com>
Co-authored-by: Ítalo Johnny <italojohnnydosanjos@gmail.com>

docs/sidebars.js

@@ -147,6 +147,7 @@ module.exports = {
         "Integrations/integrations-langfuse",
         "Integrations/integrations-langsmith",
         "Integrations/integrations-langwatch",
+        "Integrations/integrations-opik",
         {
           type: "doc",
           id: "Integrations/integrations-mcp",