GH-128914: Remove all but one conditional stack effects (GH-129226)

* Remove all 'if (0)' and 'if (1)' conditional stack effects

* Use array instead of conditional for BUILD_SLICE args

* Refactor LOAD_GLOBAL to use a common conditional uop

* Remove conditional stack effects from LOAD_ATTR specializations

* Replace conditional stack effects in LOAD_ATTR with a 0 or 1 sized array.

* Remove conditional stack effects from CALL_FUNCTION_EX