Enable PR Comments for other SCM integrations

Requires abstraction to map a "PR comment" to other SCM integrations

1. GitLab

We want to define a set of [lightweight metrics]() that SDKs can automatically collect for e.g. framework, language or platform, focusing only on signals that **do NOT overlap with Tracing**. Ideally these metrics should give a quick sense of app or runtime health, … while deeper investigation will still rely on traces or profiles.

Examples**:**

* Node.js runtime metrics (e.g., event loop delay, heap usage)
* Prisma-related metrics in Next.js
* Mobile CPU / memory usage to help surface potential ANRs or app hangs

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**Candidate Metrics (add more below)**

* …

*(please also add ideas, questions or examples in comments)*

No file, test, or entry point is named. Start by reconciling the request for PR comments across SCM integrations with the unrelated SDK metrics text, then clarify the intended GitLab behavior and the abstraction boundary. Done is not currently defined beyond supporting GitLab.

Written by the indexing model from the issue text.