Rename kitty-tool to kitten

It's easier to type, and cuter.

Also, most, if not all of the TUI parts of
kitty's kittens will eventually be re-written into kitten.

The only downside I can see is that we cant tab complete kitty
anymore, but hopefully there will be less reason to run kitty
from the shell as command line tools migrate to kitten.

Meowrrrr!!!

bypy/init_env.py

@@ -81,10 +81,10 @@ def run_tests(kitty_exe):
 def build_frozen_tools(kitty_exe):
     cmd = SETUP_CMD + ['--prefix', os.path.dirname(kitty_exe)] + ['build-frozen-tools']
     if run(*cmd, cwd=build_frozen_launcher.writeable_src_dir) != 0:
-        print('Building of frozen kitty-tool failed', file=sys.stderr)
+        print('Building of frozen kitten failed', file=sys.stderr)
         os.chdir(KITTY_DIR)
         run_shell()
-        raise SystemExit('Building of kitty-tool launcher failed')
+        raise SystemExit('Building of kitten launcher failed')
 
 
 def sanitize_source_folder(path: str) -> None:

bypy/macos/__main__.py

@@ -106,9 +106,9 @@ def do_sign(app_dir):
             codesign(fw)
             items = set(os.listdir('.')) - fw
             codesign(expand_dirs(items))
-        # Sign kitty-tool
+        # Sign kitten
         with current_dir('MacOS'):
-            codesign('kitty-tool')
+            codesign('kitten')
 
     # Now sign the main app
     codesign(app_dir)