* tests: consolidate safe ui-egui integration targets
* Group the safe UI tests as tests/ui_group/ instead of turning off test discovery
With autotests = false, a test file added later builds only if someone also lists it in
Cargo.toml, so new tests could silently never run. A tests/ui_group/main.rs target groups the
same 15 files while Cargo keeps discovering every other file in tests/.
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Co-authored-by: Brandon Thomas <echelon@gmail.com>
