Refactor flake.nix

[aleasims]

Some refactoring of flake file:

• Move derivation into separate file, simplify flake file;
• Removed explicit dev shells from flake file
• Remove unnecessary step in CI workflow;
• Remove flake-utils from Crypto3 input (because it's not used in the current revision of Crypto3. However it will have to be added later).

Most of the things work the same as previously. To activate dev debug shell, run:

nix develop .#debug

Some things which may be improved in the future:

• Refine Boost library propagation properly
• Refine the list of required Go tools (they were just copy-pasted, probably we don't need all of them)

[aleasims]

Also created targets in CMake for testing executables (block generator and assigner) runs on example data. To run these tests:

ninja executables_tests

This will compile required binaries (assigner, block_gen, ...) and run them with specified inputs.

These tests are also included into Nix check phase and will be run on:

nix flake check

This will allow us to run all tests inside single derivation via Nix and avoid re-compilation (CI time decreases: ~3min -> ~1.5min).

[aleasims]

@knazarov could you please take a look at Nix part of this PR

[x-mass]

LGTM, except we there is no way to nix develop into debug with tests. Are we sure we don't want to make default check use Debug build? In this case it could be used as a target for nix develop. Or just return back devShells with debug+tests configuration

[akokoshn]

moved to #84