Enable k2v feature flag in CI

nix/compile.nix

@@ -118,6 +118,7 @@ let
      But we want to ship these additional features when we release Garage.
      In the end, we chose to exclude all features from debug builds while putting (all of) them in the release builds.
      Currently, the only feature of Garage is kubernetes-discovery from the garage_rpc crate.
+     The experimental feature k2v is also enabled here in all builds.
     */
     (pkgs.rustBuilder.rustLib.makeOverride {
       name = "garage";
@@ -131,7 +132,7 @@ let
       name = "garage_rpc";
       overrideAttrs = drv: { /* [1] */ setBuildEnv = (buildEnv drv); };
       overrideArgs = old: {
-        /* [4] */ features = if release then [ "kubernetes-discovery" ] else [];
+        /* [4] */ features = if release then [ "kubernetes-discovery" "k2v" ] else [ "k2v" ];
       };
     })