Separate binaries and kdist in nix derivation into different outputs

[juliankuners]

When installing a nix derivation into a profile, the entire content of that output is placed into a profile directory. This currently included the generated kdist directories like, e.g., wasm-semantics, evm-semantics, etc.

Due to this, nix will fail to install a derivation if another installed derivation provides conflicting files. This can happen, e.g., when installing both komet and skribe. Nix will then throw an error like this:

$ kup install komet
 ⌛ Building 'komet' ...
warning: skipping dangling symlink '/tmp/nix-99859-0/lib/scripts'
error: An existing package already provides the following file:

         /nix/store/y3m4pakz9gxj7dp985y64karrvr8i81a-komet-42d24e605352a81523ca7ac67b782e210406d470/wasm-semantics/source/wasm-semantics/test.md

       This is the conflicting file from the new package:

         /nix/store/5vzw3cmnyk1k4d1sqhfyi11ws6ikrxx3-skribe-abfe4c931103a9de2c32526ff61966cc16734563/wasm-semantics/source/wasm-semantics/test.md

       To remove the existing package:

         nix profile remove komet

       The new package can also be installed next to the existing one by assigning a different priority.
       The conflicting packages have a priority of 5.
       To prioritise the new package:

         nix profile install github:runtimeverification/skribe/abfe4c931103a9de2c32526ff61966cc16734563?narHash=sha256-DnzUrJu4hjwHjMbO1HlzPlPGvDGmOn%2BHcR3FMQjoL40%3D#packages.x86_64-linux.skribe --priority 4

       To prioritise the existing package:

         nix profile install github:runtimeverification/skribe/abfe4c931103a9de2c32526ff61966cc16734563?narHash=sha256-DnzUrJu4hjwHjMbO1HlzPlPGvDGmOn%2BHcR3FMQjoL40%3D#packages.x86_64-linux.skribe --priority 6
Command '['nix', 'profile', 'install', 'github:runtimeverification/komet/42d24e605352a81523ca7ac67b782e210406d470?narHash=sha256-ad1PBpVWh6Kc6Nqm095ULCiD3ES0EuTBUeTEDbP8SBY%3D#packages.x86_64-linux.komet', '--extra-experimental-features', 'nix-command flakes']' returned non-zero exit status 1.

❗ The operation could not be completed.
   See the error output above (try re-running this command with '--verbose' for more detailed logs) .

This PR fixes this by placing the kdist files in a separate nix derivation output out. The binaries are placed in output bin. This is properly following nix conventions of multiple-output derivations.

A PR like this should be created in every RV nix repository, respectively. Though this already resolves every conflict between skribe and another RV nix-packaged tool.

[bbyalcinkaya]

Tested locally with kup. The fix works as expected and resolves the conflict.