refactor(3p/nix/libexpr): Use Abseil collection types for parser state r/1325

Replaces the previous uses of the (ordered!) std::map and std::set
with absl::flat_hash_{map|set}.

After some careful reading it seems that there is actually no
ordering dependency on these types, and the (drop-in) replacements
perform slightly better.

Overall this is not fixing a bottleneck, just a driveby thing.

Change-Id: Ided695dc75676bd58515aa9382df0be0a09c565e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1220
Reviewed-by: glittershark <grfn@gws.fyi>
Reviewed-by: isomer <isomer@tvl.fyi>
Tested-by: BuildkiteCI

0 files changed, 0 insertions, 0 deletions