The race detector noticed this initially in `TestAgentConfigWatcherSidecarProxy` but it is not restricted to just tests.
The two main changes here were:
- ensure that before we mutate the internal `agent/local` representation of a Service (for tags or VIPs) we clone those fields
- ensure that there's no function argument joint ownership between the caller of a function and the local state when calling `AddService`, `AddCheck`, and related using `copystructure` for now.
