nix-env -> nix profile priority: add test

tests/functional/nix-profile.sh

@@ -54,6 +54,7 @@ nix-env -f ./user-envs.nix -i foo-1.0
 nix profile list | grep -A2 'Name:.*foo' | grep 'Store paths:.*foo-1.0'
 nix profile install $flake1Dir -L
 nix profile list | grep -A4 'Name:.*flake1' | grep 'Locked flake URL:.*narHash'
+grep '"priority":10' $TEST_HOME/.nix-profile/manifest.json
 [[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
 [ -e $TEST_HOME/.nix-profile/share/man ]
 (! [ -e $TEST_HOME/.nix-profile/include ])

tests/functional/user-envs.nix

@@ -31,6 +31,7 @@ let
       // {
         meta = {
           description = "A silly test package with some \${escaped anti-quotation} in it";
+          priority = 10;
           inherit platforms;
         };
       }