…item (#5494)

### What

- Follow up to #5482
- Fixes #5232 


This PR adds support for expanding and scrolling to the focus item in
the Streams view. It also adds expanding/scrolling the Blueprint tree
when focusing on a component.

- Blocked on emilk/egui#4174

TODO:
- [x] update egui commit once ☝🏻  is merged


https://github.com/rerun-io/rerun/assets/49431240/55c2959f-bb9b-4f67-b20b-06ba82175d71


### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using newly built examples:
[app.rerun.io](https://app.rerun.io/pr/5494/index.html)
* Using examples from latest `main` build:
[app.rerun.io](https://app.rerun.io/pr/5494/index.html?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[app.rerun.io](https://app.rerun.io/pr/5494/index.html?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!

- [PR Build Summary](https://build.rerun.io/pr/5494)
- [Docs
preview](https://rerun.io/preview/e879778c92dd2e50eb05bc6fdefee9ac79b93872/docs)
<!--DOCS-PREVIEW-->
- [Examples
preview](https://rerun.io/preview/e879778c92dd2e50eb05bc6fdefee9ac79b93872/examples)
<!--EXAMPLES-PREVIEW-->
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

… to target offset (emilk#4174)

This PR fixes two issues related to `ScrollArea`.

1) When a `ScrollArea` would have `drag_to_scroll` set to `false` (e.g.
because some custom logic is at play or some other reason), it would not
animate to the `target_offset`, effectively making
`Response::scroll_to_me()` ineffective.
2) Single-direction `ScrollArea`s would leak the `scroll_target`'s other
direction. In certain specific circumstances (e.g. an horizontal area
nested in a vertical one, or inversely), this _could_ work as intended,
but in many other cases it could cause unwanted effects. With this PR,
both `scroll_target` directions are consumed by nearest enclosing
`ScrollArea`, regardless of the actually enabled scroll axes.