### What
* Part of #7378

### Issues found
* #7425
* emilk/egui#5114
* #7427

## How to test
#### Test setup - build the viewer
* `pixi run rerun-build`
* `pixi run rerun-build-web`

#### Test matrix
* Run `cargo r -p test_ui_wakeup` and test:
  * That the viewer wakes up in the background when it's alt-tabbed
* That the viewer wakes up when minimized (it should log "Received a
message from…")
* Run `cargo r -p test_ui_wakeup -- --serve` and test:
  * The viewer wakes up when browser is alt-tabbed away
* Switch to a different browser tab, send a few messages, switch back.
The messages should be there
(this is not a conclusive test, as the messages might have been received
on tab select)

## Tested

### Web
* [x] ✅ Browser alt-tabbed
* [x] ❌ Web background tab
* Has never _properly_ worked. Is blocked on
emilk/egui#5112
  * It catches up when we switch back to the tab though
       
### Linux
* [x] ✅X11 alt-tabbed
* [x] ✅ X11 minimized
* [x] ✅  Wayland alt-tabbed
* [x] ❌ Wayland minimized (Hyprland placed on non-visible workspace)
* [x] ✅ X-Wayland alt-tabbed
* [x] ✅ X-Wayland minimized (Hyprland placed on non-visible workspace)

### Mac
* [x] ✅ Native alt-tabbed
* [x] ✅ Native minimized

### Windows
* [x] ✅ Native alt-tabbed
* [x] ✅ Native minimized

### 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 examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7422?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7422?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)!
* [x] If have noted any breaking changes to the log API in
`CHANGELOG.md` and the migration guide

- [PR Build Summary](https://build.rerun.io/pr/7422)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

To run all checks from `main`, comment on the PR with `@rerun-bot
full-check`.

---------

Co-authored-by: Antoine Beyeler <49431240+abey79@users.noreply.github.com>

…k#5114)

Fix for a regression in 0.28

* `App::save` will now be called when the web app is hidden (e.g. goes
to a background tab)
* `App::update` will now be called when the web app is un-hidden (e.g.
becomes the foreground tab)