Add support for BLAKE3 hash to fetchurl

[yonas]

Is your feature request related to a problem? Please describe.
No.

Describe the solution you'd like
As an alternative to md5, sha1, sha256, and sha512, I would like to use BLAKE3.

Describe alternatives you've considered
N/A.

Additional context
N/A.

Priorities
N/A.

[SuperSandro2000]

related #2166

[yonas]

@SuperSandro2000 Thanks. I'm going to leave this open because BLAKE3 is much faster than BLAKE2 and SHA.

[AsbjornOlling]

This could be helpful for building roc programs.

Roc dependencies are pinned by a URL and a BLAKE3 hash. If it were possible to pass a BLAKE3 hash to fetchurl, then we could probably build Roc applications without needing a nix-code-generation step (like node2nix or others).

[Ericson2314]

I think this is also good for Guix store layer compat