Feed paths via stdin

[jzbor]

It is now possible to feed attic paths via stdin: zhaofengli/attic#176

This way it is no longer to chunk the paths when pushing (

attic-action/src/stages/push.ts

Line 29 in 5619ef4

const splitAddedPaths = splitArray(addedPaths, 25);

).
This should significantly speed up the action.

[ryanccn]

This is blocked until Nixpkgs' attic-client is updated to include this feature, since it is not feasible to build attic from source on every CI run.

[jzbor]

Alright! Seems like the corresponding PR is already on master, so it should not be too long: NixOS/nixpkgs#346503

EDIT: Should be in the binary cache now: https://nixpkgs-tracker.ocfox.me/?pr=346503