This adds support for verifying signatures found in NARInfo files.
This still needs to be hooked together with the nix+http[s] backend.
Change-Id: Ic1c8ddbdecfb05cefca2492808388b0f7f3f2637
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10081
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI