The impl Display for NixAttrs needs to wrap double quotes around any
keys which are not valid Nix identifiers. This commit does that,
and adds a test (which fails prior to this commit and passes after
this commit).
Change-Id: Ie31ce91e8637cb27073f23f115db81feefdc6424
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7084
Autosubmit: Adam Joseph <adam@westernsemico.com>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
