Closes #52629

## Overview

Adds a generic editor-owned navigation overlay primitive for rendering
target ranges, anchored labels, and fade ranges. This gives [Helix amp
jump](https://github.com/zed-industries/zed/pull/43733), [Beam
Jump](https://github.com/zed-industries/zed/pull/45387), and future
jump-style features (like [this
one](https://github.com/zed-industries/zed/issues/14801)) a shared
editor abstraction for overlay layout and paint instead of
feature-specific render paths.


###  Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable


Release Notes:

- N/A