Jsonnet spec defines special behavior for `super.field` and
`field in super` expressions, while in jrsonnet it is implemented by
standalone-super concept, with optimizations in case of `super.field`.
However, standalone-super is conflicting with `field in super` behavior,
so special handling is needed for this expression.
It doesn't work with the downstream nix users of jrsonnet, and may cause
security issues.
Upstream issue: https://github.com/serde-rs/serde/issues/2538