feat(tvix/eval): add scaffolding for merging nested attribute sets r/4995

This sets up the required logic for finding and merging attribute sets
into nested bindings if they exist. This is absolutely not complete
yet and can, at this commit, probably cause undefined runtime
behaviour if nested attributes are specified.

The basic idea is that a new helper function on the `TrackedBindings`
struct is called with each encountered attribute and determines
whether the new entry can be merged into an existing attribute or not.

Right now the only effect this has in practice is that a new error
becomes available if somebody attempts to cause a merge into an
inherited key.

Change-Id: Id010df3605055eb1ad7fa65241055889dd21bab0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6798
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

0 files changed, 0 insertions, 0 deletions