Handle macros more consistently: make them a proper internal keycode-style object and not a weird one-off. Fixes sanity_checker on my keymaps.

kmk/common/macros/__init__.py

@@ -1,10 +0,0 @@
-class KMKMacro:
-    def __init__(self, keydown=None, keyup=None):
-        self.keydown = keydown
-        self.keyup = keyup
-
-    def on_keydown(self):
-        return self.keydown() if self.keydown else None
-
-    def on_keyup(self):
-        return self.keyup() if self.keyup else None