ci: use crane flake to build with nix

This enables to add cargo `fmt`, `clippy` and `deny` to nix, using cached results.

Move the `teepot` crate to the `crates` subdir to make the life easier for
the `crane` flake.

Signed-off-by: Harald Hoyer <harald@matterlabs.dev>

crates/teepot/tests/data/test.json

@@ -0,0 +1,16 @@
+{
+  "last_digest": "",
+  "commands": [
+    {
+      "url": "/v1/auth/tee/tees/test",
+      "data": {
+        "lease": "1000",
+        "name": "test",
+        "sgx_allowed_tcb_levels": "Ok,SwHardeningNeeded",
+        "sgx_mrsigner": "c5591a72b8b86e0d8814d6e8750e3efe66aea2d102b8ba2405365559b858697d",
+        "token_policies": "test",
+        "types": "sgx"
+      }
+    }
+  ]
+}