Detect new EDOT Collector components in update-docs workflow

When a new release adds a component that hasn't appeared before, the automated `update-docs` PR currently silently stamps it with the current version. There's no prompt for reviewers to decide whether it should be `core`, `deprecated`, or needs an `annotations` entry in `components.yml`.

## Proposed solution
Extend the `update-docs` workflow to detect newly stamped components and list them in the generated PR body, so reviewers know to check `internal/edot/components.yml` before merging.

Implemented in #16241.

Part of #16257.