[v18.x backport] url: ensure getter access do not mutate observable symbols
Opening as draft so we can run benchmarks, if the perf looks OK, I'll open another PR to land the test on main first.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Opening as draft so we can run benchmarks, if the perf looks OK, I'll open another PR to land the test on main first.