Internal integrations - Add input for scoping webhooks per project

### Problem Statement

My webhook is noisy and firing too often. I am interested in scoping it to only accept events for some projects, but have to manually do that through the terminal.

### Solution Brainstorm

We already have the logic to scope the webhook for a specific project, or multiple projects by calling that endpoint (full steps outlined in [#85502]()). Can we add an input field or something else, inside of the internal integrations "webhooks" section to allow configuring it for select projects?


Could look like our inbound filters input, but instead nested under "webhooks" for projects.


Then send the body:

```
{
projects: ['project-1', 'project-2']
}
```

[https://github.com/getsentry/sentry/pull/85502#issue-2864731015]()

### Product Area

Settings - Integrations

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

---

**Candidate Metrics (add more below)**

* …

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

Start with the internal integrations webhooks section and compare it with the existing inbound filters input. Read the project-scoping endpoint and implementation described in issue #85502 and pull request #85502, then define completion as configuring selected projects in the UI and sending the corresponding projects list.

Written by the indexing model from the issue text.