nixos/tests/user-account: add static uid for alice

A lot of tests assume that the alice user
will have a uid of 1000. Let's make that
a guarantee and be able to reference this value.

Changed files
+1
nixos
tests
+1
nixos/tests/common/user-account.nix
···
{ isNormalUser = true;
description = "Alice Foobar";
password = "foobar";
+
uid = 1000;
};
users.users.bob =