nixos/terminfo: inherit TERMINFO* env vars also for doas

This should mirror the behavior we implement for sudo: The TERMINFO and
TERMINFO_DIRS variables are inherited from the normal user's
environment, so terminfo files installed in the user's profile can be
found by ncurses applications running as root.

nixos/modules/security/doas.nix

···
     (optionalString rule.noLog "nolog")
     (optionalString rule.persist "persist")
     (optionalString rule.keepEnv "keepenv")
-    "setenv { SSH_AUTH_SOCK ${concatStringsSep " " rule.setEnv} }"
+    "setenv { SSH_AUTH_SOCK TERMINFO TERMINFO_DIRS ${concatStringsSep " " rule.setEnv} }"
   ];
 
   mkArgs = rule:

nixos/tests/doas.nix

···
       # ../../pkgs/tools/security/doas/0001-add-NixOS-specific-dirs-to-safe-PATH.patch
       with subtest("recursive calls to doas from subprocesses should succeed"):
           machine.succeed('doas -u test0 sh -c "doas -u test0 true"')
+
+      with subtest("test0 should inherit TERMINFO_DIRS from the user environment"):
+          dirs = machine.succeed(
+               "su - test0 -c 'doas -u root $SHELL -c \"echo \$TERMINFO_DIRS\"'"
+          )
+
+          if not "test0" in dirs:
+             raise Exception(f"user profile TERMINFO_DIRS is not preserved: {dirs}")
     '';
   }
 )