Nix does it now.

This commit uses the latest version of `gargantext-graph`, now rebranded
`gargantext-graph-core`, which allowed us to drop unused dependencies
like `accelerate-arithmetic` & co.

The recommended way to build GGTX is via cabal anyway, and stack
shouldn't get in the way of a successful build.

BREAKING CHANGE: this requires a newer version of `nix-shell`, at least
2.18 onwards. You can upgrade following the steps at:

https://nixos.org/download/

In particular, these are the bumped packages:

* GHC (9.4.8 -> 9.6.6)
* Cabal ( -> 3.12.1.0)
* Fortran ( 7 -> pinned)

[worker] various fixes

See merge request !389

Replace performance-critical parts of the algorithm with `massiv` (and ditch `accelerate-llvm`)

See merge request !382

We are now around 6/7 times slower than the LLVM code.

This also changes the cabal.project to not pull the accelerate-llvm or
the llvm-hs dependencies.

There are some rounding errors in the tests, but otherwise
the implementation seems correct.

It's crucial to be able to understand the API surface area when porting
the old code to `massiv`. It turns out that other than distributional,
the other piece of code using the LLVM interpreter is
`logDistributional2`.