SetLocal should not be called during execution

[andrewyunt]

Function is called in testingutil.go and funcs.go in Sonolark

https://pkg.go.dev/go.starlark.net/starlark#Thread.SetLocal

[johnSchnake]

google/starlark-go#252 (comment) is an example of embedding the go context into the thread local storage before the run but still having the potential for it to change (ie obviously this is useful only because the context may be marked as stopped/cancelled elsewhere and that being reflected in this method).

Not quite the same as my expected workaround of embedding the context so we can add data into its databag, but similar.