Dont set the EDITOR env var in child processes

It isnt really needed, since the various kittens dont rely on it
anymore, instead calling get_editor() to get the path to the editor.
Has the nice side-effect of not needing to run the shell at startup
to read its environment. Now the shell is only run if the user calls
the edit config file kitten. Fixes #3426

kitty/cli.py

@@ -852,3 +852,10 @@ def create_opts(args: CLIOptions, debug_config: bool = False, accumulate_bad_lin
             print('Running under:', green('Wayland' if is_wayland(opts) else 'X11'))
         compare_opts(opts)
     return opts
+
+
+def create_default_opts() -> OptionsStub:
+    from .config import load_config
+    config = tuple(resolve_config(SYSTEM_CONF, defconf, ()))
+    opts = load_config(*config)
+    return opts