Fix focus behavior and provided thumb and focus color aren't applied to Cupertino variant of `Switch.adaptive` (#126688)

fixes https://github.com/flutter/flutter/issues/126637
fixes https://github.com/flutter/flutter/issues/126669

##  ~~To be merged after https://github.com/flutter/flutter/pull/126684~~

### Description

1.  Fix the Cupertino variant of `Switch.adaptive` requires two tab key presses to focus.
2.  Fix `thumbColor` & `focusColor` aren't applied.

### Before
Requires two tab presses to focus. and `thumbColor` & `focusColor` aren't applied.

https://github.com/flutter/flutter/assets/48603081/24635551-0794-443f-8320-32fdaa5de57a

### After
Single tab key to focus (no additional focus node) and `thumbColor` & `focusColor` are applied.

https://github.com/flutter/flutter/assets/48603081/9bf42fd8-c7e0-475a-b933-192a94650b0c