ci: update Nix installation and caching

This commit updates the CI workflow to use the latest versions of the
'install-nix-action' and 'cachix-action' from
the 'cachix' organization.
It also specifies the 'nixos-unstable' channel for Nix packages.

Replaces 'determinateSystems' actions with 'cachix' actions.
Configures 'cachix' to use the 'peerswap' cache.

.github/workflows/ci.yml

@@ -40,7 +40,12 @@ jobs:
         with:
           fetch-depth: 0
       - name: Install Nix and run tests
-        uses: determinateSystems/nix-installer-action@v12
-      - uses: DeterminateSystems/magic-nix-cache-action@v7
-      - uses: DeterminateSystems/flake-checker-action@v8
-      - run: nix-shell --run "make test-${{matrix.test-vector}}"
+        uses: cachix/install-nix-action@v25
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+      - uses: cachix/cachix-action@v14
+        with:
+          name: peerswap
+          authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+      - run: nix develop --profile dev-profiile 
+      - run: "make test-${{matrix.test-vector}}"